When you rinse something, you run water over it. You probably at least rinse your hands before sitting down to eat, and rinse your dishes afterward.
After shampooing your hair in the shower you need to rinse it, and many recipes call for you to rinse rice before cooking it. You can also rinse your mouth out, either with water or mouthwash. When it's a noun, rinse means the act of rinsing, or a hair treatment: "After the red rinse, you'll barely recognize yourself." Rinse shares the Latin root recens, "fresh or new," with recent.