A private tracker is a website that has the same functionality as a public tracker but restricted behind an invite. The advantages of a private tracker are retention, quality control, selection, speed, security. animebytes would be the best private tracker for anime.

They’re just like public trackers, but private so you’ll generally need an invite to get access to them. They generally are much better than the public trackers. Not sure about an anime specific one though.

Private trackers are great since people tend to seed things for longer, also to note generally keeping your ratio up is required. Personally, I use a private tracker when I need to find something I just can’t find anywhere else, but with that said for anime nyaa should be the only place you really need.