Intro to Specific Chess Openings

It's important for an improving player below 2000 to remember that the key to doing well in the opening is remaining alert, watching out for tactics (while spotting errors made by the opponent) and quickly developing your pieces. That is to say it is not about memorizing random lines. Knowing how to avoid a trap on move 4 in an Open Game that could easily cost you large amounts of material/the game is infinitely more important than knowing a line in the Slav (Closed Game) 12 moves deep for a tiny advantage, that will never even get played at your level. However, there are general patterns and tactical motifs that regularly keep appearing in certain openings. As such you should know the positional/tactical nuances of some key positions.  

Following general opening theory, there are four types of games that arise; Open Games, Semi-Open Games, Closed Games and Semi-Closed Games. In addition there are flank openings and irregular openings. I have a brief introduction of each below, but I will also expand on them in other posts.

Again the openings themselves are not that important (except in the actual repertoire you are using). What is important is learning the tactical motifs and the plans related to openings so you can improve your piece play, strategy, and tactical vision quickly.

Open Games begin with 1. e4 e5. There are many sharp lines that may arise. While white is in the driver seat being half a move up in a symmetrical position, black has many fighting chances as well. There are lots of tricks and traps for both players. You should play e4 with White and reply against e4 with e5 as black if you're under 20000 and want to improve your chess quickly. Note that above 1500 trying out c5 (the Sicilian Defense) against e4 is alright. 

Semi-Open Games begin with 1. e4 but Black does something else besides e5. The most popular Semi-Open Game is the Sicilian Defense in which Black does 1...c5 (pictured below). Some open-games such as the Sicilian are more tactical/sharp while there are other options by Black that are more positional in nature. 

Closed Games begin with 1. d4 d5. The nature of the position, with the center pawns both being defended by the Queen, makes these positions a lot less tactical in nature compared to open games. People under 2000 simply should not play this as White if they care about rapid improvement as the positional advantages that you get are often too subtle. As Black you can get away with just playing 1...d5 followed by 2...e6 against virtually whatever White does and easily achieve a good game.

Semi-Closed Games arise after 1. d4 Nf6. Similar to Closed Games  you can easily make 2000 without really caring about these too much. However you may decide to play one of these as Black when White does play d4.  

Flank Openings begin with 1. c4, 1. Nf3, 1. f4, 1. g3, or 1. b3. Some of these lines transpose into types of Closed and Semi-Closed Games. These can easily be ignored but some patzers get addicted to them. When you do get to 2000 perhaps revisit 1. Nf3.

Irregular Openings are other things not often played. Again you can ignore them. I'll just post about them a little because they have funny names.

Side note: When I say a position is sharp it means that their is often only a limited amount of playable moves in the position and that failing to play the best options will lead you to losing lots of material fast. For example below, with it being Black's turn,

for a beginner I would classify the Scholar's Mate as being sharp, if Black just does a random move like h6, he will simply lose next turn after White plays Qxf7 checkmate. 

Below is an example of a subtle position.

Note how Black can make any move without losing material. White simply does not have tangible threats in the short term.