What is a Meet and Greet pass at a Jonas Brothers concert?

It really depends on whether you have a backstage ticket, or not. Also if those people have said that they'll meet and greet the crowd after the show, or before.

The smaller the show, the easier it is to meet the bands. If there are less then 1000 people, usually the bands will come out after the show to talk to fans and sign Autographs. At larger shows, this is more uncommon, and there tend to be special meet and greets only for members of a paid fanclub.