The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above and below the surface of the Earth. The mass water on Earth remains fairly constant over time but the partitioning of the water into the major reservoirs of ice, fresh water, saline (salty) water and atmospheric water is variable depending on a wide range of climatic variables. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid (ice), and gas (vapor).
Numerous websites exist which have great graphics and animations depicting the water cycle. Some of these are the U.S. Geological Survey's (USGS)The Water Cycle (the source of the graphic below) and NASA's Water Cycle.
Of course, we're partial to the animation of the hydrologic cycle (starts at about 5:30) contained in Surfrider Foundation's Sea to Summit video: