An IP is a unique identifier for each device on a network. Its primary purpose is to allow devices to communicate with each other. IP addresses are somewhat comparable to a postal address. In a common household setup, you may have multiple devices connected to a single internet connection through a router. All these devices would get the same external public IP Address. If one of these devices is connected to the internet through a wireless carrier, it would have a different IP address than a device connected to your home router.