Cisco IP unnumbered inside

What is IP unnumbered? In Cisco routers, the ip unnumbered <other_interface> command allows you to borrow the IP address of another interface. Although the Cisco help page [http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094e8d.shtml#unnumbered_iface] explains in detail how to