Networking with Linux is not always as simple as you might want, especially if you don't have a GUI. The assumption here is that you don't. One great place to start is How to configure CentOS with a static IP and DNS - Server - Sebastiaan de Jonge's Blog, which covers the important issue of DNS resolution in /etc/resolv.conf.
The file /etc/hosts is the standard hosts file, mapping hostnames to IP addresses. Some people like to add their local hostname to this file, if that is you then just add it to the end of the line beginning 127.0.0.1 for IPv4 and/or the line ::1 for IPv6.
Running system-config-network on CentOS helps configure the network, both DNS and adapter config.