DHCP is Dynamic Host Configuration Protocol. It basically allows you to connect to a DHCP server [similar to BOOTP], and tell it to configure your network settings, including gateway, ip address, dns address etc.
The DHCP package basically includes a client [and sometimes a server] for DHCP - do you need it? It shouldn't prevent Gnome from working okay though. Oh, and /etc/hosts is where the mapping of hosts > ip addresses is, if you want to use names without a dns server