DHCP stands for Dynamic Host Configuration Protocol. DHCP is used in networks to configure computers (hosts) connected to that network so they can communicate via IP addresses.
Your internet service provider (such as your broadband provider) operates DHCP servers, with your modem being the client.
The data on IP addresses and their corresponding domain name is listed and maintained on the DHCP server. When you join a new broadband provider, the DHCP server allocates an IP address for you, and sends configuration information to your modem.
A client’s IP address assigned by a DHCP server is usually for a limited time period, with IP addresses needing to be renewed before expiry to continue with the same configuration.