IP address
An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
An IP address serves two principal functions: host or network interface identification and location addressing.
Mobile IP
The Mobile IP allows for location-independent routing of IP datagrams on the Internet. Each mobile node is identified by its home address disregarding its current location in the Internet. While away from its home network, a mobile node is associated with a "care-of" address which identifies its current location and its home address is associated with the local endpoint of a tunnel to its "home agent". Mobile IP specifies how a mobile node registers with its home agent and how the home agent routes datagrams to the mobile node through the "tunnel".