Trackers with private group of people with ussually better digital stuff, better organised, with admins, who actually care about development of their community, cause they're paid through donations, which give advantages to users like vip status or gigabytes to your ratio (download/upload), which is like a precaution to avoid poeple to just hit and run torrents, and it's hard to get in cause you need invite from someone within or get through open day opportunity, which is never or rarely, depends on the admins of tracker.