A mattress protector is a protective layer covering the entire mattress, shielding it from liquids and fluids. A mattress pad is an additional layer of padding covering the top layer of the mattress. Here are the main functional differences.
Mattress ProtectorMattress Pad Covers the entire mattress, stretching from corner to cornerCovers only the top layer of the mattress Protects the mattress from liquids, dust, bugs, and moistureWorks as an extra layer between the mattress and the sleeper Does not provide extra paddingProvides extra padding for added comfort Helps protect mattress qualityDoes not protect mattress quality