Level and Profession Restrictions
Characters on a trial account are restricted to Level 20. If your character reaches level 20, you can still continue playing the game; however, you will not earn any experience from completing quests, defeating enemies, participating in battleground fights or any other source of experience. Additionally, characters on a trial account can't increase their skill in any profession beyond 100.
Gold and Trading Restrictions
Characters on a trial account are limited to owning 10 gold per character. Additionally, those playing on trial accounts may not purchase or sell items through the auction house or trade directly with other players, either through face-to-face trading or through the mailbox.
Communication Restrictions
Characters on a trial account may not use any public chat channels, such as trade or general, or any player-created chat channel, although they can still communicate with other players using the say, party and whisper channels. Additionally, a character on a trial account is restricted to whispering only to other characters who have added him to their friends list or who have whispered to him first. The voice chat and RealID communication features are also disabled for all trial accounts.
Group and Guild Restrictions
Characters on a trial account may not create a guild or join an existing one. Additionally, if you are playing on a trial account, you may not invite other characters to a group. To join a group, you will have to wait to be invited. As well, you may not be invited to a group that contains a character above Level 20.
Considerations
The restrictions to trial accounts are quite severe because they are designed to limit the use of trial accounts by people whose only aim is to advertise gold selling, power leveling and other services that are against the game's terms of service. Despite the restrictions, creating a trial account can be a good way of deciding if purchasing the full version of "World of Warcraft" and setting up a monthly subscription is worth the expense.