The term Dynamic DNS, or DDNS, describes a mechanism with which a DNS system is automatically updated as soon as the associated IP address (or domain) is changed.
A classic application of DDNS is when a host with a public IP must be in perfect correspondence with the same domain name.
In order to work, a DDNS requires a client to be installed on the host which owns the interested IP address or, as an alternative, it’s often integrated with the firmware of gateways and routers.