What type of compound is CH3COOH?

This is a conjugate base to the weak acid called Acetic acid, CH3COOH.

CH3COO- is called: Acetate ion.
This is the conjugate base of the weak acid Acetic Acid, CH3COOH.

It is commonly called an Acetate anion or just Acetate.

Ethanoate is the official IUPAC name.