Rolling edit helps you speed up your editing process when you have to adjust clips. Once you hover at their intersection point, you'll see a new button up here. You can drag that button for example to the left, thus lowering the duration and endpoint of the first clip and increasing the duration and the endpoint of the second clip. You can use it in movies where for example, you have one movie with a tiger and another movie with a snowboarder. And you can increase the size and the point in this number. Their movie that does no border starts while decreasing the tiger movie.

I'm sorry Tiger fans.