A siphon is a simple device used to move liquids from one container to another, typically using gravity. It consists of a tube that is bent in a U-shape, allowing liquid to flow from a higher level to a lower level. The process begins by filling the tube with liquid and creating a vacuum, which allows the liquid to flow through the tube and out of the other end. Siphons are commonly used in various applications, such as transferring water from a tank to a garden or draining liquids from a barrel. They rely on atmospheric pressure and gravity, making them an efficient and easy way to move fluids without the need for pumps.