Used, as the name implies, to power jet engines. Although this was the sole original use of the fuel (powering aircraft), modern vehicles may use it in a number of applications. Due to its use in equipment other than aircraft turbojets, it is sometimes referred to as turbine fuel. Other applications include:

As EdSausage has noded, there are many types of jet fuel. They differ in composition (distillation type, additives, coloring, etc.) depending on their intended use. These range from cold-weather types, to naval aircraft, to ship fuel, to commercial aviation. Their designation or name varies depending on context and locale, but some include:
Thanks EdSausage!