What is "mattress protector"

n. An item of removable bedding that sits on top of or encases a mattress to provide protection to the mattress.

A mattress protector is an item of removable bedding that sits on top of, or encases, a mattress to protect it. Some mattress protectors also provide protection to the person sleeping on the mattress from allergens and irritants such as dust mites, bed bugs, mold, and dead skin (like dandruff).