The new "checks" screen that appears just before you publish your video on YouTube is a preliminary check that YouTube performs to make sure that you haven't uploaded content that infringes on someone else's copyright. Presumably, these checks are performed by some magic algorithm crafted in the bowels of the Google machine.
These new copyright checks could be helpful in making sure that you haven't accidentally infringed on someone's copyrighted material before it goes public.
Via Gumersindo Fernández