1
General chess
Most Important Chess "General Principles".
2
Tactics
There are many ways to describe chess tactics, but perhaps the simplest is to say that a chess tactic is a move (or series of moves) that brings an advantage to a player.
3
Opening, Middlegame, Endgame
The game might be divided into three parts, i.e.:- 1. The opening. 2. The middle-game. 3. The end-game. There is one thing you must strive for, to be equally efficient in the three parts. Whether you are a strong or a weak player, you should try to be of equal strength in the three parts.