Not quite. I used to be a mentor. Took a few months off from the forum during which time I also ceased being a mentor. Once I returned to the forum I took a few weeks to ensure that I was going to be sticking around before finally giving in to An t-iasg about considering becoming a mentor again.
Below I've tried to give an overview of the various roles on Aquarium Advice. I might be slightly off on some of the rights of each group, but it should give you a pretty good idea of the difference between Admins, Moderators, and Mentors.
Mentors are members of the forum that have demonstrated that they are knowlegable about the hobby. They take an active role helping out other members to get started, figure out problems, etc. They do not have any sort of administrative authority on the forum (can't move threads, split posts, merge posts, deal with spammers, etc.), but because they take on the role of helping to ensure that the questions are getting answers they do free up the moderators and admins to spend more time on those adminstrative tasks.
Moderators are the ones that make sure that things keep running, by keeping things in order, reminding members to act within the forum guidelines, moving threads to the appropriate location if posted in the wrong forum, etc.
The Admins are the owners of the forum. They are the ones that get into the guts of the code and provide us with all the enhancements to the software, take care of viruses, ban users that act inappropriately, etc.