A "swamp cooler" is a cooler made by blowing air over water. The water absorbs heat in order to evaporate, which also increases humidity. I believe the pads are

A "swamp cooler" is a cooler made by blowing air over water. The water absorbs heat in order to evaporate, which also increases humidity. I believe the pads are replaceable porous sponge material to increase the surface area exposed to the air.