Here's a list of restrictions in the free-to-play version:
A level cap of 20. A maximum of 10 gold. Trade skills are capped at 100 ranks. Unable to trade via the Auction House, mailbox, or player-to-player. In-game access to public chat channels unavailable. Players are limited to communicating using only say, party, or whisper. Characters will be unable to create or join guilds. Characters are not able to send whispers to other characters unless they have been added to the characters' friends lists or have received a whisper from a character first. Characters will not be able to invite other players into a party. Characters will not be able to join parties with other characters above level 20. Voice chat disabled on Starter Edition accounts. Realms experiencing login queues will prioritize players who have full, paid accounts. Starter Edition accounts are not eligible for character transfers RealID features are disabled on all Starter Edition Accounts.