The network provides access to a wide collection of resources. Most computers today connect to the network either through an Ethernet network card or else by modem. Once connected you have an IP address (and sometimes more than one) assigned to your computer by which all communications is effected. IP addresses are sequences of numbers.
Two things need to happen to get your network going: loading a driver for your network card and specifying your network address and configuration.
An Ethernet based network is usually started up at boot time by the system initialisation script /etc/init.d/networking. For pcmcia network cards the /etc/pcmcia/ tree provides its own scrips, including /etc/pcmcia/network, that is called whenever a network card is found in the PCMCIA socket.
Your IP address bitwise ANDed with the so called netmask yields your network address. The network address bitwise ORed with the negated netmask yields your so called broadcast address. The IP address of the router through which you connect to the Internet is referred to as the gateway.
A simple example is:
IP: 192.168.0.34 (0xc0a80022) Mask: 255.255.255.240 (0xfffffff0) Network: 192.168.0.32 (0xc0a80020 = 0xc0a80022 & 0xfffffff0) Broadcast: 192.168.0.47 (0xc0a8002f = 0xc0a80020 | ~0x0f)