Anyone know about second look interviews?

I've recently heard about them and not sure how prevalent they for IM programs? Are they more for the applicants to re-visit the program and see if she/he really wants to go there or more for the programs to see which applicants are really interested in their programs.

What does the usual second look interview day look like? Is it like another regular interview day or do you get to see the real day of an intern in that program?