The fountain is a juggling pattern that is often used for juggling an even number of objects. In a fountain, each hand juggles separately, and the objects are not thrown between the hands. For example, in a four-ball fountain, each hand juggles two balls independently.
A fountain can be synchronous or asynchronous. In a synchronous fountain, both hands throw at the same time, while in an asynchronous fountain, the hands alternate throws. The fountain can also be juggled in columns, where the balls all travel vertically up and down, and are caught from where they are thrown, or round in a circle, so that they are caught close to the body and thrown from either side of it (or vice-versa).
The fountain is used for juggling even numbers of objects because other patterns which alternate between hands (such as the cascade) do not work well for even numbers. In fact, a true cascade is impossible with an even number of objects, although there are several patterns such as the shower that can be performed with even numbers.