Server

Servers are computers that hold files, programs and the network operating system, they provide access to resources to all the users of the network, and servers are often dedicated, meaning they perform no other tasks besides their server tasks.

Modem

A modem or “modulator” gives you the ability to an internet connection over the existing phone line. A modem is not necessary for a Local Area Network but it is required for other internet connections such as DSL or dial up. Modems convert the analogue data from the phone lines into digital data so that it can be interpreted by computer systems, ADSL modems can be used on many different types of networks; they provide the necessary connectivity to the internet.

Gateways

A gateway is generally a combination of hardware and software with the ability to perform protocol conversions; gateways are able to connect networks that use c different protocols or data formats but they are slower than a bridge or router though its activities are more complex as a gateway can use multiple protocols.