@Swinly Using it allows you to make sure that your project actually fits on your material and that it will carve where you want it to.
I think if you go here
Chris shows it in action. I say “think” because I am running another application in my PC that takes over the audio, so I can’t run the link to confirm what I think is there.
If I’m wrong, L, let me know and I will take some time to find what I know is here somewhere.