Swing your right foot forward and land, balance. Now swing your left foot forward and land, balance, then back to your right and repeat. Not that difficult, afterall you have been doing it since you were a kid, but is that all there is to running? Yes.
However, it is not all there is to Running. The repeated collision with the ground as you move can take a toll on your body, fortunately your body is prepared to deal with it. That does not mean that injury does not happen, but it means that you can do something about it.
Check back here for suggestions for keeping your running body running.