A network is a collection of computers and other devices that can send data to and receive data from one another, more or less in real time. A network is often connected by wires, and the bits of data are turned into electromagnetic waves that move through the wires. However, wireless networks transmit data using radio waves; and most longdistance transmissions are now carried over fiber-optic cables that send light waves through glass filaments.
A network program is any application that uses a computer network to transfer information to and from other applications. All of these pieces of software share the ability to communicate with other computers, and in so doing, become more useful to the end-user and secure. Users generally trust network applications; therefore, these programs have much greater control over the computers on which they are running than a Web site has over the computers viewing it.