Agitators are devices used to mix or stir fluids in various industries such as chemical, food, pharmaceutical, and cosmetic industries. They can be used to mix liquids together, promote the reactions of chemical substances, keep homogeneous liquid bulk during storage, and increase heat transfer (heating or cooling) . There are different types of agitators, including mechanical agitators (rotating), static agitators (pipe fitted with baffles), rotating tank agitators (e.g., a concrete mixer), paddle type mixers, agitators working with a pump blasting liquid, and agitator turning tanks to gas. The choice of the agitator depends on the phase that needs to be mixed (one or several phases): liquids only, liquid and solid, liquid and gas, or liquid with solids and gas.

In the context of washing machines, agitators are tall spindles, vaned or finned, that twist back and forth, rubbing against clothes to help break apart stains. They are a part of the washing machine found in the wash basket. In contrast, washing machines with impellers use a low-profile cone or disc that spins/rotates to rub clothes against each other to get them clean.

In summary, the use of an agitator depends on the industry and the specific application. In washing machines, agitators are used to help break apart stains, while in other industries, they are used to mix or stir fluids.