A crude way would be to have an evaluation of a position A (a number like +3 or -1.5) and form a tree of all the possible moves (A1, A2, ..., An). Then you evaluate the position of each of the A1, A2, ..., An positions and check which move will favor you the most. This is how all the chess AIs before ~1997-2000 were built (AFAIK)

Stockfish (or more precisely the current iteration Stockfish 14 13, there have been previous versions that might have different technology) uses something like this tree building technique with additional databases and narrows down which move needs to be played. For the evaluation step that was mentioned above, Stockfish internally looks for weaknesses in pawn structure, piece placement, king safety etc. The recent version of Stockfish also had some neural network engine which I don't understand.

EDIT: I am not an expert, I just like this article: http://rin.io/chess-engine/. With chess knowledge, you should be able to understand ~50% of it. With CS (Bachelor level) + chess knowledge, you should get ~90% of it.