Faucets come in a staggering array of styles, colors, and shapes--but they all do the same thing--turn water on and off--pretty much the same way.
A compression faucet, common particularly in older homes, has a washer or seal that cuts off the water flow by closing against a valve when the faucet is turned off. These tend to drip from the spout when the washers wear out. With compression faucets, hot and cold are controlled with two separate handles.
Other faucets called "washerless" don't have washers but do have O-rings that provide a seal. They have a cartridge, ball, or disc mechanism that controls the water flow.
Disc faucets have a movable upper disc and a fixed lower disc; raising the upper disc makes the water flow, and lowering the disc shuts it off.
Cartridge faucets have a metal or plastic insert that seals the spout. Ball faucets are operated by a lever that aligns a slotted ball with inlets in the faucet. Most washerless faucets mix cold and hot water and have a single handle, though disc faucets may have two separate controls.
