The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol networks whereby a DHCP server dynamically assigns an IP address and other network configuration parameters to each device on a network so that it can communicate with other IP networks. It operates based on the Client–Server model.
For example, in your home network, the DHCP server on your router can dynamically assign an IP address to your phone (DHCP client), so that your phone can connect to the network and communicate with other devices. Without DHCP, you will need to assign IP addresses for all the network devices manually.
All the Reolink cameras/NVRs support the DHCP protocol (as DHCP client) and can obtain the IP configuration from a DHCP server.
And Reolink WIFI NVR and PoE NVR can work as a DHCP server to assign the IP address to the devices connected to NVR.
For a more detailed definition of DHCP, please refer to: Dynamic Host Configuration Protocol