Objectives
Like other games, chess has a set of objectives one can have that determine how the game is played.
Check for checks
The endgoal of the whole chess game is to checkmate the opponent's king. To do this, you must first check the king. This is done by moving a piece in such a way that the king is in check. This means that the king is in a position where it can be captured by an opponent's piece. Which is why it is important to keep looking for checks to gain advantage of ending the game in your favor and early on.
Check for captures
While the endgoal is to checkmate the opponent's king, capturing is very helpful in reaching that endgoal as it diminishes the chances of the opponent to win against you. Some of their pieces might be blundered, or in other terms "oh! a free piece!". Capturing helps you gain material. Material is the value of the pieces on the board. The more material you have, the more likely you are to win the game.
Check for attacks
If the two objectives won't apply to your turn, then checking for attacks is the next best thing. Attacking is a way to gain advantage over your opponent. It is a way to gain control over the board. It is a way to gain material. It is a way to check the king. It is a way to checkmate the king. It is a way to win the game. Attacking generally is a way to create potential tension on the board for your opponent. By creating these threats, you can get into the mind of your opponent and make them overthink their moves. This is a very important skill to have in chess. Creating attacks is also a good way to create traps.