Networks
What a network does
A network is two or more devices connected so they can share files, printers and an internet connection. A LAN (local area network) covers one building or site; a WAN (wide area network) spans cities or countries, and the internet is the largest WAN of all. In a client–server network a central server supplies services and controls access; in a peer-to-peer network devices share directly with each other, with no central controller.
Know the job of each box of hardware. A modem converts the signal on your provider's line into something your equipment can use. A router shares one connection among several devices and directs traffic between your network and the internet. A switch joins devices inside a single wired LAN. A wireless access point extends the LAN over Wi-Fi, and a network interface card is the hardware that lets a device join the network at all. The ISP (internet service provider) sells you the connection.
Each device on a network has an IP address used for routing; DNS translates human-friendly names such as a website address into IP addresses. Bandwidth is how much data can flow per second - it is capacity, not the same as latency, which is delay.
Traps to watch: the internet is not the same as the World Wide Web (the web is one service running on the internet); an intranet is an internal private network, while an extranet gives selected outsiders controlled access; and a modem is not a router, even when one box does both jobs.
Rule of thumb: modem = translates the line, router = shares and directs, switch = joins local devices.