The Dynamic Host Configuration Protocol (DHCP) is a set of rules used by communications devices such as a computer, router or network adapter to allow the device to request and obtain an IP address from a sever which has a list of addresses available for assignment.

DHCP is a protocol used by networked computers (clients) to obtain IP addresses and other parameters such as the default gateway, subnet mask, and IP addresses of DNS servers from a DHCP server. The DHCP server ensures that all IP addresses are unique, e.g., no IP address is assigned to a second client while the first client's assignment is valid (its lease has not expired). Thus IP address pool management is done by the server and not by a human network administrator. ---by http://en.wikipedia.org