From Diablo Wiki
Clickables refers to objects in the game world that can be clicked, or hit by spells, to produce some action. Things like chests, hollow logs, dead bodies, barrels, loose floor tiles, and many more such objects are clickable.
Most clickables are destructibles, and will active from a distance when hit with a spell.
In Diablo III there are also clickable triggers, such as chandelier chains or crumbling walls, that will collapse or trigger falling objects. These do not emit loot, but are basically traps that damage monsters in the vicinity.