When a machine asks a DHCP server to assign it an IP address, its asking for a lease on an address for a certain amount of time. When the lease expires the client can ask the server to renew its lease.
In DHCP, a lease concept is employed where a machine requests an IP address from a DHCP server for a specific duration. When the lease period expires, the client has the option to request a lease renewal from the DHCP server.
