Imagine you are in the centre of a football pitch and you stand on the point where the kick-off takes place. There is this white circle around you, let’s call it the nucleus and let’s call the football an electron. The electron is bound to the nucleus, meaning it moves in some trajectory around (and sometimes in) the nucleus. If we would measure the distance from you to the ball at some certain time intervals and place this in a sort of histogram with distance on the x-axis and counts on the y-axis. If you would look at this histogram or distribution (as given in the video), you would see that the electron spends some time inside the circle or nucleus. The last step is then to realise that the nucleus is a 3D object and we have to change the circles to spheres and realise the electron can move in 3 dimensions in and around the nucleus.