AntiCheat tries to make player classification as simple as possible while still allowing admins to have as in-depth player analysis as they see fit. AntiCheat implements different classification levels of players that refers to the probability that they are using hacked clients. By default, these are Low, High, and Medium. These levels can be changed in your configuration.
Most players stick in the Low range, as you would guess, but you can explore a live list of which player is in what group by typing /anticheat report. In addition, if you have the admin permission, when a player's level goes up into a new group, you will be notified in chat of the change.
Remember that just because a player is in medium or high does NOT mean they are hacking, sometimes I find bugs that get a normal player up to those levels in a matter of seconds by doing something that the plugin assumed was not legal, when in fact it was just a regular part of the game. When I find a bug like that I typically fix it ASAP, I don't let them lay around, but you should also be cautious, make sure to question and/or follow players who hit these levels to get the real story.
For information on commands use /anticheat help.
To view information about a certain player use /anticheat report [username]. This will show you checks that this user has failed.
To view information about a certain group use /anticheat report [groupname]. This will show you users that are in this group.
To view XRay statistics for a player, including how much of a certain block they are breaking, how likely it is that they are using xray, and other info, use /anticheat xray [username].
To forgive a player use /anticheat reset [player], and their hack level will be reset back to 0 (low).
To view debug information use /anticheat debug. This will generate a report on pastebin.com for you to view that includes information that might be helpful in fixing issues, or getting help from developers. This information is anonymous and cannot personally identify your server, and is safe to share with others.
Updates are pushed to AntiCheat automatically and you never have to worry about updating it as long as you have auto-update turned on in the config. Turning it off will require you to manually download builds to stay protected. If you have this setting set, you can use /anticheat update to see if there is a new update available.