A unique string of numbers separated by periods that identifies each computer attached to the Internet. Any machine connected to the Internet has an IP address: Xbox , phones, fax machines etc... In every case, the IP address acts both like a car license plate and like a telephone number: it shows ownership, allows the machine to be located by other machines, and empowers authorities to track and protect people's safety.
Your computer sends your IP address to every website you visit. That is a normal part of how your web browser works.