A network, in computing, is a group of two or more devices that can communicate. In practice, a network is comprised of a number of different computer systems connected by physical and/or wireless connections. The scale can range from a single PC sharing out basic peripherals to massive data centers located around the World, to the Internet itself. Regardless of scope, all networks allow computers and/or individuals to share information and resources.

Computer networks serve a number of purposes, some of which include:

• Communications such as email, instant messaging, chat rooms, etc. 
• Shared hardware such as printers and input devices 
• Shared data and information through the use of shared storage devices 
• Shared software, which is achieved by running applications on remote computers

Some of the basic hardware components that can be used in networks include:

• Interface Cards: These allow computers to communicate over the network with a low-level addressing system using media access control (MAC) addresses to distinguish one computer from another.
• Repeaters: These are electronic devices that amplify communication signals and also filter noise from interfering with the signals.
• Hubs: These contain multiple ports, allowing a packet of information/data to be copied unmodified and sent to all computers on the network.
• Bridges: These connect network segments, which allows information to flow only to specific destinations 
• Switches: These are devices that forward, make forwarding decisions and otherwise filter chunks of data communication between ports according to the MAC addresses in the packets of information.
• Routers: These are devices that forward packets between networks by processing the information in the packet.
• Firewalls: These reject network access requests from unsafe sources, but allow requests for safe ones.