Most rainfall results in overland runoff.

Runoff

Runoff is nothing more than water "running off" the land surface. Just as the water you wash your car with runs off down the driveway as you work, the rain that Mother Nature covers the landscape with runs off downhill, too (due to gravity).

Even though some rainfall soaks into the ground, most of it flows over the land surface, going downhill. This runoff water reaches rivers, lakes, and the oceans, keeping the water cycle going.

Runoff is also important because as it flows over the land, some of it soaks into the ground, thus "recharging" groundwater, providing plants with water for their roots to take up so they can create the delicious beets and spinach you like so much, and keeps underground aquifers (areas underground full of water) full so people can drill a well and pull the water out for their own purposes.