A “nude” is pretty much what it sounds like a picture of yourself in the nude/naked, usually in the form of a selfie, a self-taken picture. Now if someone asks you to send nudes, you have two options: Send nudes if you are comfortable with sending a picture of your naked body to.
Nudes are what girls that are desperate for attention pass around school. Also popular with exhibitionist girls with enormous egos that love to show off.
Send nudes is a request, usually from a man, for naked pictures, usually of a woman and often on social media, internet dating services.