The time average position of the electron can be illustrated by observing this electron at different times. If one were to for example note down the position of the electron with a dot every 30 seconds. If you would do this for a long enough time, there would be areas where there are more dots and areas with less (or even no) dots. The areas with the most dots represent the areas where the electron spent the most time while areas without (or with less) dots would represent places were the electron is (almost) never present. We can then after enough time say that the areas with the most dots represent what we call the time-averaged position of the electron.