Learn with Thomas & Oscar. This RYA Video shows how to tie a reef knot, one of the knots needed at stage 2. As Thomas says, it's good for reef points (remember those?), sail ties and tying up you brother. This is not a very secure or useful knot for sailing, and only works if the two ropes are of the same thickness.
Here is an animated video showing how to tie the reef knot and a few variations. More information on the Animated Knots website.