That ride at the fair that spins you around until you stick to the walls? The device in your washing machine that spins your clothes around quickly to get the water out of them? Those are centrifuges.
Centrifuges are used mostly in science. In this application, centrifugal force — the force from spinning that moves things away from the center — separates liquids that have different weights. For example, a centrifuge is used to separate blood cells from plasma cells. When the blood is spun in the centrifuge, the heavier plasma cells separate from the lighter blood cells, and can be collected for other uses.