What is structure and function of the body covering of amphibians?

It is covered in skin. This skin excretes a mucous layer which keeps it moist and also acts in protecting the animal from pollutants. Some amphibians can also breathe through their skin, although most have lungs for breathing.
The skin is glandular and contains both mucous and poison glands but lacks external structures such as scales, feathers, or hair, characteristic of other groups of tetrapods.
Amphibians are characterised by having a body covering of moist skin.