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: Description, Bio, Homepage, Multiclass, Returnclass, Advancewizard, Advancetier, Score, Who, Title, Save, Quit, Socials, Help, Hlist, Status, Sleep, Wake, Rest
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
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.
Mobmaster - Selects a target mob to hunt and slay, gives progressive experience bonuses and gets progressively more difficult
Quest - Assigns a target to slay near your current effective level and gives a time to complete the task, if completed you receive quest points which can be used to buy prizes.