I (Tens) am creator of this game and there are admins on each server. I did not make any of the admins, the host of each server did. Normally an admin's job is to keep out people trying to destroy the server or break rules. But since the host (which is just a regular player who hosts a server) is the one making the admins they do whatever the hosts tells them usually.
Some admins are good but don't be surprised if the admins are very abusive and just out for power. You have to choose a good server where they won't abuse you just for fun.
Hosts are just regular players who choose other regular players to be admins for the server and I have nothing to do with it.
Admins have tons of commands that can do tons of different things.