Planetouched feats are feats that a character may acquire after having spent a certain period of time on a plane of existence which is not the dimension she was born into. Oftentimes, a character might pick up some essence of the plane she has been to, or learn some new ability that would not otherwise available if she had not interacted with the denizens of a particular realm.
Adventurers in general might gain some affinity for the plane or it’s denizens. Sorcerers and magi might find that they suddenly have a clearer grasp of spells which originate from the plane they have been exploring. Rogues traveling on the plane of shadow, for instance, may find that they are able to move through shadows in other dimensions much easier. Warriors might learn new fighting styles derived from the horrors they encounter in their otherworldly travels.