/etc/resolv.conf contains a list of DNS servers

nameserver 192.168.1.108
nameserver 192.168.1.1
search linuxit.org

/etc/HOSTNAME or /etc/hostname is used to give a name to the PC

One can also associate a name to a network interface. This is done in differently across distributions.

/etc/hosts contains your machine's IP number as well as a list of known hosts

# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1      localhost  localhost.localdomain  
# other hosts 
192.168.1.108  mesa  mesa.domain.org  
192.168.1.119  pico

/etc/sysconfig/network defines if networking must be started. (can also contain the HOSTNAME variable)

NETWORKING=yes
HOSTNAME=mesa.domain.org
GATEWAY=192.168.1.1
GATEWAYDEV=

/etc/sysconfig/network-scripts/ifcfg-eth0 The configuration parameters for eth0

DEVICE=eth0
BOOTPROTO=none
BROADCAST=192.168.1.255
IPADDR=192.168.1.108
NETWORK=192.168.1.0
ONBOOT=yes
USERCTL=no

/etc/network/options is used on Debian-based distributions to hold general networking options

/etc/network/interfaces is used on Debian-based distributions to hold interface configuration information.

# configure the loopback interface
auto lo
iface lo inet loopback

# configure the Ethernet interface and gatewat
auto eth0
iface eth0 inet static
        address 192.168.1.108
        netmask 255.255.255.0
        network 192.168.1.0
        broadcast 192.168.1.255
        gateway 192.168.1.1