The Socratic method is a way to clarify how the person reached a certain conclusion, or lead them to the realization that the previous conclusion was wrong.
It takes the form of dialog, so you ask a series of questions to probe deeper and deeper until you reach the destination. In a sense it is similar to 5 whys.
It can be quite useful in reviews of all sorts, 1 on 1s, and mentoring.
One caveat to keep an eye on is that the whole thing can sound patronizing or pedantic. So it must always come from a place of curiosity, not condescension.