The DHCP service automatically assigns IP addresses to clients that reside in a defined subnet. In the DHCP server configuration, you can define address pools and explicitly map MAC addresses to a reserved IP address. You can also define additional parameters that are passed to the client when an IP address is requested.
The DHCP Relay service forwards DHCP broadcast messages to other network segments. DHCP relaying allows you to share a single DHCP server across logical network segments that are separated by a firewall.
For more information, see How to Configure the DHCP Relay Agent.