. Stands for Modulator and Demodulator.
  . Used for data transfer from one computer network to another computer network through cables.

Why Modems?

  . Computer network works in digital mode but data is carried in analog mode.
  . So data must be converted into analog before sending and digital before using.
  . This is done by Modems.
  . At transmitter, it works as Modulator.
  . At receiver, it works as Demodulator.

Modems and Routers:

  . Modems are connected to routers to create local area network to connect devices.
  . Router passes internet connection to all the devices in the network.
  . We don't need a router if we want internet connection to single device.
  . Router serves as wireless access point so that internet connection is distributed to devices like phones, tablets through wifi.
  . A modem/router would have modem with builtin router in a single device.