Hoppers somewhat erratically hop around and don't move very quickly. They have the capability to stack themselves on top of each other, thus allowing the Hopper on top to traverse tall obstacles. They can be picked up and thrown with telekinesis, and they hurt you upon contact. They also get destroyed if thrown against another solid object or enemy.
Super Hoppers are nearly identical to Hoppers except they jump higher and are a bit faster.
"Hoppers are a bit more erratic than robots, which makes them harder to use effectively in puzzles. They do have some pretty cool emergent behavior though."