In the states I've lived in, its a piece of paper you keep in your wallet alongside your previous DL/permit that's now been hole-punched. You use both together

In the states I've lived in, its a piece of paper you keep in your wallet alongside your previous DL/permit that's now been hole-punched. You use both together to serve as your proof of authority to drive if you get pulled over. Of course, only until the real DL arrives in the mail, which usually takes a week or two.