The base Guild Wars 2 game is now free, meaning you don't have to purchase it to play anymore. There are a few restrictions though. Free players will start with less bag slots and character slots than regular paid accounts. There is no map wide chat, and whispers are allowed every 30 seconds (to different people).
You can also access the trading post, but cannot mail stuff to other players. WvW is restricted to L60 on free accounts. For more information and to play for free, check out the official Guild Wars 2 site.