The water cycle is driven by energy from the sun in the form of sunlight.
Sunlight warms the surface of the earth and causes water to evaporate from the oceans, lakes, rivers and other sources of surface water.
Once in the atmosphere water vapour may condense to form clouds which may subsequently produce rain and snow (precipitation) returning water to the land and the oceans.
Water that falls on the land as rain and snow will eventually travel via lakes, streams, rivers and so forth back to the oceans thus completing the water cycle.
The key processes in the water cycle are
About 86% of the water entering the atmosphere by evaporation comes from the oceans, but only about 78% of precipitation falls on the oceans, thus there is a net transfer of water from the oceans (via the atmosphere) to the land. Run-off from the land eventually returns this water back to the oceans.