Commands generally do exactly the the name implies, however if you ever have any questions simply type HELP followed by the command you want to learn more about in-game to get more information (HELP STORE for instance) The following is a list of some (though not all) of the more important commands for a new player to know.
Exploration: Look, Exits, Examine
Directions: North, South, East, West, Up, Down, Northeast, Northwest, Southeast, Southwest, Enter
Items & Equipment: Get (Take), Inventory, Equipment, Junk, Donate, Sacrifice, Compare, Put, Fill, Empty, Buy, Sell, Auction, Store, Wear, Remove, Wield, Hold, Repair
Character Related, Bio, Homepage, Multiclass, Returnclass, Advancewizard, Advancetier, Score, Who, Title, Save, Quit, Socials, Help, Hlist, Status, Sleep, Wake, Rest, Practice, Train
Experience: Kill, Consider, Flee, Wimpy, Cast
Communication: Channels, Gossip, OOC, Newbietalk, Racetalk, Muse, Tell, Say, Reply, Note, Shout, Yell
Magical Items: Recite, Zap, Brandish, Quaff
Staff list: Wizlist
Character development: Level, Practice, Train
Customization: Config, Prompt
PK: Bounty, Bribe, Paybounty, Obscure, Pkstat, Where, Range
Following: Ftell, Finfo, Roster, Victories, Gsend, Pray, Worship, Apostatize, Fdeposit
Rankings: scoreexp, scoreinv, scoremobm, scoreqp, scorepk, scoregold, scoremk
Convert - Converts 50 practice sessions into 1 training session.
Deposit/Withdraw - Deposit gold for safe keeping into bank account.
Ranking - See the various rankings