A DHCP server offers network configuration information on a local network. This releases the end-users from figuring out how to configure their PC for the network. It enables the network administrator to (re)configure the client computers without leaving his/her desk.
Configuration information is leased from the DHCP-server. The lease-information is stored in dhcp.leases (in /var/lib/dhcp3 in debian systems). If for some reason the DHCP configuration gets garbled, you can remove individual leases from this file, forcing the server to deliver a fresh lease to the client.
RADVD
The linux Routing Advertisement Daemon for ‘stateless autoconfiguration’ in IPv6 LANs is provided by radvd. Radvd is not a DHCP server, it assigns IPv6 addresses following RFC4291 to nodes in a LAN.