Water is important to you in many ways. Drinking water is very important for you because your body is mostly water. If you didn't have water in your body, you would look like a raisin. This is because a raisin is just a grape that has most of the water removed.
Most water comes from the oceans.
The sun causes the water to evaporate and go into the atmosphere, the winds bring the water over the land. Once over the land, the water comes down as rain, snow, hail, or sleet. When the water hits the ground, some of it goes into the ground and some is used by plants which then transpire it back into the air, the rest runs back to the oceans through rivers, streams and channels. This never ending process is called the water cycle. As you can see water has to come from somewhere and goes someplace else.