But why is it a blunder/innacuracy?

It doesn't appear that you have played any games here. It would be easier to help you if there were a game that you could point to as an example.

How can you tell? Just because of the name….. because there’s tons of people named Josh (sorry if that’s not your name joshimitsu29) in the world who could be asking the exact same question… ‘But why is it a Blunder/Inaccuracy?’

Why is what a blunder and inaccuracy?

Inaccuracies do not exist.
Either a move changes the game state drawn / lost / won or it does not.
If it changes the game state, then it is a mistake, not an inaccuracy.
If it does not change the game state, then it is not inaccurate.

Inaccuracies obviously do exist.

An accurate move in any theoretically winning position is one that reduces the minimum number of ply to force mate against accurate play by the opponent, i.e. depth to mate (DTM), by 1. (Well defined because that minimum number of ply is finite in a theoretically winning position.)

In a theoretically drawing position an accurate move is synonymous with a perfect move (i.e. a move that doesn't produce a theoretically losing position).

An inaccuracy is just a move that is not accurate. An inaccurate move may or may not be also a blunder (a move that changes the theoretical evaluation).

Inaccuracies that are not blunders can lead to sub-optimal results under basic rules (no 50M/3R rules). E.g.  White has a theoretically winning position below (whoever has the move).

If White adopts the strategy of alternately moving his king between h7 and g8 that is only a drawing strategy, it neither mates nor loses.

Nevertheless all his moves are perfect, the position up to any point in the ensuing game remains winning for White. The game state doesn't change; the problem is that all his moves are inaccurate.

Inaccuracies also play a large part in practical play with the 50M/3R rules in effect. It is usually more difficult to win a longish mate the closer the DTM is to the the number of ply remaining under the 50 move rule. Inaccuracies by the winning player reduce the difference between the two without shortening the mate; they are a major factor in players failing to win KBNvK, KQvKNN etc. from winning positions.

(I think the word "blunder" is more frequently used than "mistake" to denote an imperfect move. Both terms are used in other senses in chess literature, but "blunder" at least usually denotes a bad move. The term "mistake" can mean almost anything, e.g., "1...c5 as a response to 1.e4 might be a mistake against an expert on the Sicilan if you haven't studied the opening".)

A blunder (??) is a gross mistake or double mistake that changes the game state from won to lost.

'I have attached question marks to the moves which change a winning position into a drawn game, or a drawn position into a losing one, according to my judgment; a move which changes a winning game into a losing one deserves two question marks ... I have distributed question marks in brackets to moves which are obviously inaccurate and significantly increase the difficulty of the player's task ... There are no exclamation marks, as they serve no useful purpose. The best move should be mentioned in the analysis in any case; an exclamation mark can only serve to indicate the personal excitement of the commentator.' GM Robert Hübner

He mentions neither "blunder" nor "mistake".

Some people use a single exclamation mark to denote the only accurate move in an endgame and a double exclamation mark to denote the only perfect move in an endgame (if it's not an endgame, in most positions nobody really knows, but the symbols are still liberally used and often a double question mark annotates a half point blunder).

The best explanations will come from showing the position to stronger players and asking them the *why* questions. Folks get some decent results doing that on these forums. You could do the same.

It would be much better if you'd show a game that you have trouble with.

Generally, there are 2 main cases:

1. Your move a blunder because it's bad. If the opponent finds the right answer, you lose.

2. Your move is not bad, but a much better move is available instead.

To find the "why", you'll need to switch to the Analysis tab ("Game review" is worthless, you can't find out anything there), and see how the engine evaluates various moves. If you don't understand what's going on, make a move and see what the engine recommends. You can do this, going back and forth as you like, until you are satisfied.

"Blunder is subjective. You can have a game where you have 2 moves:

1. Mate in 1

2. Capture the queen

Capturing the queen will be labeled a blunder. But you're a queen ahead.

Taking the queen would actually be a miss, because say the two rooks were threatening mate, and the queen could take the queen technically your just going to win with extra material…