It's a plastic clip witha suction cup.
You it to the inside of the aquarium glas and then you can "clip" the veggies to it so they don't sit on the bottom of the tank.
It does work with most fish, but I would still recommend letting some veggies sink if you have bottom feeders.
Bottom feeders may come up to the clip, but it really is better for them to forage the substarte.
CM