Characters on Starter Edition game licenses have the following restrictions:
Can't play expansion-restricted content (new classes, continents, etc).
Can't exceed level 20, 10 gold, and 100 trade skill ranks.
Can't participate in Pet Battles.
Can't chat in channels other than say and party.
Can't whisper another character unless they add you to their friends list.
Can't create or join guilds, invite players into a party, or create calendar invitations.
Can't disable experience gains.
Can't trade, mail, or use the Auction House.
Can't use voice chat or Real ID.
Can't use value added services (character transfers, faction changes, etc).