A mock interview is a rehearsal: someone asks you real interview questions, you answer them properly rather than in your head, and you get told what landed. It works for the same reason a dress rehearsal works. The first time you say an answer out loud it comes out badly, and it is far cheaper for that to happen here than in front of a hiring manager.
That is what separates this page from a list of questions. Our behavioral interview questions tool is a prep sheet: it gives you questions with model STAR answers up front, to read before you practise. This one is the rehearsal loop. It asks one question, waits for your answer, scores it, and only then moves on. Use the prep sheet first if you have never written a STAR answer, then come back here and say them.