Grouping allows you to take multiple clips and group them together so that they behave as one unit. For example, I have a section like this one, which I've worked on for a long time, and I don't want to mess the synchronization up. So I grouped all the clips together so they stay lined up perfectly. Basically, I select them right click and select group. Now they behave like one unit, they move like one they act like one to ungroup them, you just have to right click on them and select ungroup. If you don't want to accidentally make changes to your clips, you can lock your clips down.

For example, if you have music in the background, you probably don't want to get out when you're editing your video. So you can right click on it and select lock clips. The clips fade to gray and they can be moved or split. To unlock just right click on any locked clip and select Unlock clips