Chess is not a solved game and there are no optimal moves outside of given situations, so mastery depends on situational awareness and general knowledge. Players must learn to evaluate things such as their board position and the likely outcomes of given moves before they can start to garner advantage in chess.
A game of chess comprises three separate stages. These are the opening, the middlegame, and the end game. The opening is crucial to setting up positioning that pays off in the middlegame when attacks and counterattacks create webs of cause and effect that begin stripping the board of pawns and offensive power on both sides.
It is vital at all times for a chess player to be aware of the entire board and of likely futures. Learning the moves and counter moves that dictate chess is an organic process acquired over a long period of play. It consists of techniques, not move sets, and relies heavily on observational skill.
A skilled chess player must know when making a move that the move garners the most possible advantage, particularly in the middlegame. It is hard for novice players to see where the opening will leave them in this segment, so developing opening move sets and learning common sets is a good way to gain control.