You made it to the interview stage! Your grad school application has passed the barrage of admissions scrutiny, so congratulations on making it this far — but you’re not in the door yet. The interview is where you get to really show who you are and what you can do.
Interviewing for grad school is a two-sided process. Each side determines if the other is a good fit. There has been much due diligence on each party’s behalf, so there’s clearly a connection. However, the interview is set up to answer any lingering questions so you can both see beyond what’s on paper.