Mass creates distortions in space time. Have you ever dropped a coin in those charity boxes where the coin rolls in a loop as it falls to the bottom? The distortions are like the hole in the bottom and bodies in space are the coin being pulled down. Because there is no friction in space the bodies slow imperceptibly and just keep circling for astronomical periods of time. There are also interactions across massive bodies, imagine the coin could jump across to different charity boxes and loop around different holes before jumping back again. That is my basic understanding, I am not a smart man but I believe Newton and Liebnitz were. Their explanations have lots of maff, aren't complete explanations but are apparently close enough to explain what we see happening.