The time average of the posistion of an electron is simply the most likely position for an electron to be found. If we would look at our electron multiple times we would probably find him in a different place each time.Now if we would do this enough we would be able to get a decent understanding of the most likely places an electron could be. In the case of a 1s electron we would see that probability of finding an electron only depends on the distance from the nucleus which means that they form shells around the nucleus where each point on a shell has the same probability of finding an electron as anoter point from that same shell.