A network is a group of computers (often called nodes or hosts) that can share information through their interconnections. A network is made up of the following components:
Computer systems (nodes or hosts).
Network devices that enable connectivity (such as hubs, switches, and routers).
The transmission medium provides a path for electrical signals between devices.
Network interfaces are devices that send and receive electrical signals.
Protocols are rules or standards that describe how hosts communicate and exchange data.

Despite the costs of implementation and maintenance, networks actually save organizations money by allowing them to:
Consolidate (centralize) data storage
Share peripheral devices like printers
Increase internal and external communications
Increase productivity and collaboration

One way to classify networks is based on the role network devices play:

Network Type Description
Peer-to-peer In peer-to-peer networking (also called workgroups), each computer controls access to its own resources. Security controls on each computer identify who can have access to the computer's resources. Advantages of peer to peer networks include: Easy implementation
Inexpensive
Disadvantages of peer to peer networks include: Difficult to expand (not scalable)
Difficult to support
Lack centralized control
No centralized storage

Windows 7 includes a new feature called a HomeGroup. The HomeGroup is a simple way to create a peer-to-peer network for sharing files and printers. Client/server In client/server networking, shared resources reside on special computers called servers. Other computers, called clients connect to the server to access resources. Security controls on the server identify which clients can have resource access. Advantages of client/server networks include: Easily expanded (scalable)
Easy support