Fighting means that you use your powers to actually defeat the other person playing the other character. That other player gets to use their powers to try to defeat you. Both players are equally matched in levels, and potentially have an equal ability to defeat the other.
Droning means that one player uses his Teleport Foe power to teleport a player into an area of the PvP map that players of that faction aren't supposed to go, and that player is killed instantly. The teleported player has no ability to use their powers to try to defeat the teleporting character. The teleporting player has basically killed you instantly, without earning anything for it, and the teleported character gets XP debt (what you normally get for being defeated in PvE).
Also, CoH doesn't have PvP servers, they have PvP zones. Every server has the same zones that PvP can happen in, from Arenas to full maps where everyone is matched in level. It's not like in WoW or other MMOs where PvP can happen anywhere, and the other faction can invade your territory. There are even zones where the two factions can team up together, and are a LOT more popular than the PvP zones.