It uses alpha-beta pruning[0], which requires an evaluation function. Stockfish traditionally used a man-made evaluation function, but added a small type of NN called an NNUE[1] for better results. The actual search method is still the same, though.

[0]https://en.wikipedia.org/wiki/Alpha%E2%80%93beta_pruning

[1]https://www.chessprogramming.org/NNUE