At today's Overwiev, Ben Miller, Game Designer on Guild Wars 2talks about the traits system. Traits wasn't available at Guild Wars, so what are them?

At a basic level, traits make you better at what you choose to do. You slot traits in order to modify skills and attributes. Once you have mastered a handful of traits they become a key component in creating your overall build. You acquire traits by completing profession challenges scattered throughout the world. For instance, you walk into an inn and persuade a shadowy stranger into telling you a rumor about a mysterious tome full of arcane knowledge. Or you challenge a legendary swordmaster to a duel while exploring Divinity's Reach. Each profession focuses on different activities to develop his or her traits. Warriors train physically, bash stuff, eat stuff, and drink stuff. Elementalists, on the other hand, seek ancient knowledge locked in tomes or particularly powerful elemental locations. The different trait challenges accentuate the unique feel of that profession and really bring the experience of playing that profession to life.

You can read the full Overwiew here: RPGz.org