An adapter is a device that allows a specific type of hardware to work with another device that would otherwise be incompatible. Examples of adapters include electrical adapters, video adapters, audio adapters, and network adapters.
An electrical adapter, for instance, may convert the incoming voltage from 120V to 12V, which is suitable for a radio or other small electronic device. Without regulating voltage through an adapter, the incoming electrical surge could literally fry the internal components of the device. Most consumer electronics have adapters attached to the plug at the end of the electrical cord. Whenever you see an plug surrounded by a large box, it is most likely an electrical adapter. You can typically find the input and output voltage printed directly on the adapter. A device that does not have an adapter on the end of its electrical cable typically has a built-in voltage adapter. For example, desktop computers typically have the adapter built into the internal power supply.
Video adapters and audio adapters adapt one type of interface to another type of connector. For example, a DVI to VGA adapter allows you to connect theDVI output of a laptop to the VGA input of a projector. Most professional audio devices use 1/4" audio jacks, while most computers have 1/8" "minijacks" for audio input and output. Therefore, 1/4" to 1/8" audio adapters are often used to import audio into computers. Likewise, an 1/8" to 1/4" adapter can used to output audio from a computer to a professional audio system. Since a large number of audio and video interfaces exist, there are hundreds of audio and video adapters available.
Network cards, or NICs, are also called network adapters. These include Ethernet cards, internal Wi-Fi chips, and external wireless transmitters. While these devices don't convert connections like audio or video adapters, they enable computers to connect to network. Since the network card makes it possible to connect to an otherwise incompatible network, the card serves as an adapter. Similarly, video cards are sometimes called video adapters because they convert a video signal to an image that can be displayed on a monitor.