-The network card is very fundamental to the PC system. As soon as you plug it into the network you are now nothing more than a node/workstation. It is to say the least our outside world connection to the network. The NIC will allow you to make your computer even better than before. Just think about your modem for instance. It allows you to connect to other networks using the TCP/IP protocol to view this material you are reading now. Your computer is networked to something that allows it to be bigger and better than itself, kind of neat isn't it? Your NIC is simply a translator in your PC and helps figure all out between the network and your system. Networks transmit data in Serial format to your workstation and then your NIC will convert it to parallel format for your system. If you have read through ports section your know that the serial format sends data 1 bit per transmission and the parallel moves it in 8 bits per transmission. We need to be able to change it over so that it makes since to your PC and the network your talking to. This conversion happens in both directions so don't worry too much about it.
-A NIC card can be picked up really cheap these days and you will commonly find it as a 10 baseT or 100 baseT. Something else to throw in is the connection to the NIC itself. Most LAN's use UTP (Unshielded Twisted Pair) wiring which uses a RJ-45 connector (cat5 cable). This is typical on a cheaper 10 card. Some better cards will also boast what's called a BNC (Bayonet Naur Connector) which is found mostly with coaxial cables, much like your cable TV.
