A moisturizer is a cream or lotion you put on your skin to make it less dry. Shops sell face moisturizer, hand moisturizer, body moisturizer. British spelling is often moisturiser, with an s; both spellings name the same bottle.

The verb is moisturize: to add moisture or help skin keep it. The -er here means “the thing that does the job,” like toaster. Though actually a moisturizer does not work quite like a toaster. A toaster makes toast. A moisturizer helps skin hold water; it does not magic a dry face into a wet one in one second.

Lotion, cream, and moisturizer overlap on the shelf. Moisturizer is the one that tells you the job. A sunscreen may also moisturize, but we still call it sunscreen because that is its main work.