Your IP address is a unique number assigned to your computer's internet connection by your internet service provider (ISP). This unique number serves as the ID for your connection when you access the internet.
An IP address functions like your street address — if someone wants to send you mail or you order a pizza, your address is needed for the postman or delivery person to find your home. Similarly, your IP address is used to route information from the internet to your computer.
Depending on the type of ISP service agreement you have, the IP address is assigned to your computer's connection on a provisional basis and usually changes whenever you reboot your router.