I hope this is allowed...

So I was looking through a couple of icon rating communities and the like and I kept seeing the name of "cut-out icons." I tried to do a search and couldn't find anything, and I looked at a bunch of the entries and submissions in different communities that included these, but couldn't for the life of me figure out just what they were. Can anyone either explain them to me or point me to a tutorial that does that?

Sorry to bug everyone and please, feel free to delete this if it's off topic. I'm just curious.