In what is essentially a reworking of their existing trial system, Blizzard has removed the 14-day limit and moved it to the level 20 marker. On a trial account (free to create along with a Battle.net account), you can now make as many characters as you want (10 per realm) and play them up to level 20 each. If you decide to pay for a subscription, you’ll lose the ability to “play for free”. Meaning, people who have cancelled their subscription or let them expire, won’t be able to make “free” characters on their accounts, only on new seperate trial accounts (you can have multiple WoW accounts on a single Battle.net account however).
The trial account limits are still in place, mainly: you can only have 10 gold; tradeskills are capped at 100; you can’t use the mailbox; auction house or trading; you can’t join or create a guild; you can’t invite anyone to a party; no voice chat; longer login queues; no RealID features. So in other words, you can make a character, muck about by yourself for a while to see if you like it, try other classes, etc.
While this doesn’t really change much, it does represent the first time Blizzard has reworked its “demo” version of the game. Removing the 14 day limit does give people more time to experience Azeroth and see if they like what it has to say; you’re not pressured into getting as far as you can in the time provided. You can also try out Burning Crusade races, Blood Elf and Dranei, without having to purchase Burning Crusade.
You can create a Starter Edition account on the official site.