Basically skin

If you're somewhat intelligent, you may know what the word "Integument" means. If not, that's okay! It just means skin or what naturally covers an animal, like fur. Frogs have moist thin skin for respiration and protection. Most of them need to stay moist or they could suffocate. This is why they have mucus glands! Another reasons frogs are gross. Basically, mucus is excreted to keep the skin moist whilst they are in air for gas exchange. That's why Benjamin looked slimy. Some frogs have bad tasting skin, and others are poisonous to keep predators from eating them.