DHCP
Dynamic Host Configuration Protocol. Addresses and options handed out on the LAN so you do not type them.
DHCP leases IPv4 configuration, and DHCPv6 does the v6 cousin: address, mask, gateway, DNS resolvers, sometimes boot and vendor options. A rogue DHCP server on a segment is how clients get a lying resolver or gateway.
The DNS servers you ship in DHCP are a control. If you do not define them, someone else will. Lease logs are inventory. Authorised DHCP in Windows-land is not a full security program, but an unauthorised server should still make you look.
See also: DNS, Network address translation, VLAN.
Fact source: IETF RFC 2131, DHCP.