What are campaigns, and how do you participate in them? I notice that some of the best gear is sold by campaign vendors on the fleet, but I have no idea what kind of commendations they want. They seem to want only one of... something, but they are unclear as to what. All explanations gratefully received.

Campaign gear is one of the highest tier endgame gear in the game. The tokens used to purchase campaign gear are gotten through hard mode Explosive Conflict and defeating the Voss world boss.