Concepts (Or another popular term "opening principles") are a way to guide your choice of moves. They aren't infinite but I can't say that you can narrow it down because you can produce an exception for every rule. When you learn concepts over moves, you will have a good idea of what to do in a position (based on the pawn center, how pieces are developed, and other factors), without knowing what the book move is for that position.
What are the 'concepts' of chess?

Concepts are things like space, position, attacking vs defence, lines of attack, weak or strong squares, kingside vs queenside, and lots more.
When I have an aggressive opponent, hypothetically, perhaps he's on an early kingside attack, my defensive moves are not all reactive. I keep in mind to try and defend in a way to optimize my chances to counter attack on the queenside at some point.
It often pays off, but it can take a lot of nerve or practice or both, to pull it off and not lose hope.
After 40+ years of playing chess, I just roll with it, but not so much decades ago, or even 10 years ago. I would lose most of my hope against a crushing attack.
At your level, you could get a lot out of Reassess Your Chess by Jeremy Silman.
Most people agree a used copy of the 3rd edition is your best option. The 4th edition got panned. I used the 3rd edition years ago.

When mathematically precise computational logic and memorized analysis is elusive or absent, the player is left with “concepts.”
In general, the use of “concepts” ought to give a particular player an advantage against another player with similar brute computational skills and memorized knowledge, but who doesn’t know these so-called “concepts.”

The concepts in any domain represent abstract mental models that serve as a tool for making decisions. Humans develop simple mental models to navigate thru all the complexity of life.
When we get started in chess, or elsewhere, the most general concepts should be the first thing to get familiar with. They should be the foundation of the entire chess edifice to build later.
Unfortunately, chess hasn't yet clearly defined its basic paradigm. Chess is a complex system and as such share the same aspects defining:
1) Members and their properties,
2) Members' interactions/roles/functional relationships/structural network
3) Members's collective direction/purpose/intents/goals
I've written about this in more detail in the Principia Scacchorum sequel on my blog

"Concepts" is an incorrect term, so all the previous can be disregarded.
The correct term is "Elements" - what makes for the game.
There are Four - similar to the Four Elements of matter ... Earth, Wind, Fire and Water
There are Four Elements of chess ... Space, Force, Time and most importantly Pawn Structure - Aron Nimzowitsch

To learn chess is to understand the Elements.
To begin learn the 3 principles - Control the center, Develop the pieces and King safety (usually Castle)

There are Four Elements of chess ... Space, Force, Time and most importantly Pawn Structure -
The four primary elements of chess. These are the subjects of two excellent, and well known, chess books...
Play Winning Chess by Yasser Seirawan...
https://www.amazon.com/Play-Winning-Chess-Yasser-Seirawan/dp/1857443314/ref=sr_1_3?crid=14Q5GDF6KDLQ&keywords=play+winning+chess+by+yasser+seirawan&qid=1572756134&s=books&sprefix=play+winning%2Cstripbooks%2C200&sr=1-3
New Ideas In Chess by Larry Evans...
https://www.amazon.com/New-Ideas-Chess-Larry-Evans/dp/B0000CJZEH/ref=sr_1_1?keywords=0486283054&qid=1572756342&s=books&sr=1-1

I often hear experts saying that you should learn concepts rather than moves. It's difficult to get one's head round how concepts can be completely divorced from moves, since moves ultimately comprise chess, so what are the concepts of chess? Can they be narrowed down a definite set, or are they as infinite as chess itself?
Opening Principles.
Knights before bishops.
Rooks behind passed pawns.
Passed pawns must be pushed.
Knights make great blockaders.
2 rooks are worth more than a queen.
Just to name a few...
+1, concepts are generally more promising rules for winning but they always have exceptions.
Learn basic concept-----》 break it. Learn win by breaking concepts, learn loss by breaking concepts .Make new concepts.
This is how evolution works. In other words, you will eventually make own concepts when you learn your own mistakes and improve yourself.

I often hear experts saying that you should learn concepts rather than moves. It's difficult to get one's head round how concepts can be completely divorced from moves, since moves ultimately comprise chess, so what are the concepts of chess? Can they be narrowed down a definite set, or are they as infinite as chess itself?
Concepts, in chess, are a general notion of how to evaluate a situation or what to do next, typically based on the static attributes of a position. For instance, the estimated numerical values for pieces, or a Knights' ending is similar to a King and Pawns ending, or the pair of Bishops is an advantage when their mobility isn't restricted and there are pawns on both flanks.
From a pedagogic point of view, teaching them to beginners makes sense because they're easy to remember and are valid for most situations lacking activity and, or unbalancing factors.
That said, you should consider that most of those "principles" were formulated and developed over a century ago, and most have been reformulated, such as "it's a weakness in our camp only if the opponent has time (tempos) to influence our game by playing against it", or "a good position which can't evolve into a better one isn't a good position".
As it is today, in masters' practice those principles are regarded as useful as long as they promote Piece Activity, which is highly dependent on Coordination and Time. When those principles go against activity, coordination and time, they're ignored because they contradict the position's inner logic.
An example (annotations by GM P.H. Nielsen):

Indeed. At anyone's level, playing the "right way" is number one. It's not a concept, nor should one think of Chess in such a rigid way. Opening moves (besides basic opening play), a string of a combination of moves (utilizing basic tactical play) or strategic maneuvering (basic positional themes) etc are a homogeneous whole (of "concepts"). But you needn't concern yourself with all that. Take one move at a time. Dominate a rank or file. Focus on overloaded pieces. Lock up your pawn majority on the wings. A knight is better with pawns on one side of the board. Establish a blocked center in anticipation of a Kingside attack. Give your opponent 3 pawn islands. Stuff like that is far easier to think about instead of a grand concept.

It's difficult to get one's head round how concepts can be completely divorced from moves, since moves ultimately comprise chess
Well sure, there's something to be said for a strong ability to calculate coupled with good calculation habits, but trying to play move by move is futile for our puny brains.
So we apply concepts. Maybe think of it like a shortcut. It's simply about maximizing the probability that something good will happen. An easy example is piece activity. If your pieces influence many more squares than your opponent's, then by sheer force of numbers you're more likely to have a winning tactical opportunity.
This is particularly useful for beginners who are not good at calculation yet, and will be able to apply general concepts to all sorts of positions.
deaf_blue_bottles is absolutely right. General concepts and principles don't change, they are valid in all positions (not as the nonsensical rules of thumb like "knight on the rim is grim"). He also mentioned men activity. Again to the point. The concept of power chessmen possess is the main concept. Understanding the power structure pieces establish on the board, how that power is exchanged with the other army, how it is combined against the enemy is critical chess skill.
The concepts don't give us solutions. But they serve to orient ourselves in any position and give us instinctive hints about where to direct our attention. Once we grasped the essence of the position, moves come quite naturally.
As Carlsen put it, his intuition tells him what to do. Calculation is just double check.
Last year I had a debate with GM Seirawan @gmyaz on what is "older", concepts and ideas, or moves, after his public "Nimzovich's ideas were all rubbish."

@RoaringPawn Piece activity and precise calculation are not general principles nor shortcuts but methods to get inside a position's inner logic, pawn structures don't define a position but help to understand its inner logic by abstraction, precise calculation isn't double-checking but acknowledging that general guidelines and intuition can be dead wrong in unbalanced and active situations, and while not all Nimzowitsch's ideas were rubbish he was mistaken when assuming that a strategy could be imposed regardless of the situation on the board.
General concepts and principles do change because they've been proven as misguiding in too many situations. Whole systems were considered faulty under those generalities, such as the King's Indian with Black's pawns on d6 and e5 against White's on e4 and d5 because of the assumption that with a bad Bishop on g7 and lack of space Black shouldn't be able to oppose to White's supremacy on the Queenside. When Taimanov–Najdorf was played it was a slap in the face for all those defending the "general principles" (and that was 66 years ago!):
Not getting up-to-date is anyone's choice, but promoting it means more people won't understand the game in Post #17 nor the following one:

General concepts and principles do change because they've been proven as misguiding in too many situations. Whole systems were considered faulty under those generalities, such as the King's Indian with Black's pawns on d6 and e5 against White's on e4 and d5 ...
Principles typically don't change, that's exactly what they are, they come first. Contrary to what you say, they give us guidance and orientation without providing ready solutions that only concrete assessment of the specific position does.
And what chess concept does your KID example talk about?
Seems we're not on the same page what (chess) concept is.
Can you give me just one chess concept or principle the way you see it?

Oh, we're not on the same page, not in the same book, not in the same year. Your posts and wording remind me so much of Tarrasch's "Dreihundert Schachpartien" (1896 I believe).
Because of his teachings, at one point people said that calculation was unnecessary because the principles told it all. Should you understand the principles you're talking about, you may see that according to them White has a clear strategic advantage in Taimanov–Najdorf after 8.d5, because of his solid pawn center, space advantage in the center and Queenside, and Black's bad Bishop in g7.
My stance on concepts or principles? What about a backward pawn leaving a strong central post for the enemy? Let's see what Lasker thought about it:
An example alone may not be worth. How about Capablanca's stance on conceding central space (d6 pawn vs. e4) plus a pawn to make it merrier?
Both games were annotated by Kasparov, so you have concrete proof of Carlsen, Najdorf, Stockfish's programmers, Kasparov, Lasker, and Capablanca not sharing your opinions. Then it's not me alone leaving the XIX Century's wisdom where it belongs.
I often hear experts saying that you should learn concepts rather than moves. It's difficult to get one's head round how concepts can be completely divorced from moves, since moves ultimately comprise chess, so what are the concepts of chess? Can they be narrowed down a definite set, or are they as infinite as chess itself?