With networks based on TCP/IP (which includes the internet), every device requires an identifier that uniquely identifies it. This identifier is called an IP address. This IP address can be manually assigned, but doing so for large networks (including the millions of devices connected to the internet) is simply not practical. The Dynamic Host Configuration Protocol, or DHCP, addresses this by allowing a device to have its IP address automatically assigned (along with other settings like DNS servers). For end users this process is mostly transparent - they simply connect to a network and automatically receive the appropriate IP configuration, which then allows them to participate on the network.