A sound card is a piece of computer hardware that deals with the input, output and processing of sound in the digital domain. Many computers have audio capabilities built in, while others require sound cards if audio capability is desired. Gamers quite often desire a sound card with higher specifications than the standard on-board sound device can provide, such as 5.1 surround sound or better equalization control. Also with an increase in quality of affordable home recording equipment and software more and more musicians are choosing to record at home, creating a greater need for high quality audio processing. Features a recording may look for in a sound card are low/zero latency, high bit rate processing, up to 96kHz sampling rate.

A typical sound card includes a processor, featuring a digital-to-analog converter, that converts recorded or generated digital waveforms into an analog format and vice versa. The quality of this digital to audio converter (DAC) plays an important part in the quality of the resultant audio.

This signal is led to a connector (typically 1/8-inch jack plug) where an amplifier, headphones, or similar sound destination can be plugged in. More advanced designs usually include more than one processor to separate duties between digital sound production and synthesized sounds (usually for real-time processing of audio and sound effects utilizing little data and CPU time).

Digital sound reproduction is usually achieved by multi-channel DACs, able to play multiple digital samples at different pitches and volumes, optionally applying real-time effects like filtering or distortion.

Multi-channel digital sound playback can also be used for music synthesis if used with a digitized instrument bank of some sort, typically a small amount of ROM or Flash memory containing samples corresponding to the standard MIDI instruments. (A contrasting way to synthesize sound on a PC uses "audio codecs" for example the widely used VST/VSTi plug-ins, which often heavily processor intensive, for music synthesis. This approach has become common as manufacturers seek to simplify the design and the cost of the sound card itself).

Almost all sound cards have a line in connector where the sound signal from a cassette tape recorder or similar sound source can be input. The sound card can digitize this signal and store it (controlled by the corresponding computer software) on the computer's hard disk for editing or further reproduction. Another typical external connector is the microphone connector, for connecting to a microphone or other input device that requires a relatively lower voltage than the line in connector. Input through a microphone jack is typically required for speech recognition software or Voice over IP applications.

Sound cards for computers based on the IBM PC were uncommon until 1988, leaving the internal PC speaker as the only way early PC software could produce sound and music. The speaker was limited to square wave synthesis, leading to the common nickname of "beeper" and the resulting sound described as "beeps and boops".

Several companies, most notably Access Software, developed techniques for digital sound reproduction through the PC speaker; the resulting audio, while functional, suffered from distorted output and low volume, and usually required all other processing to halt while sounds were played. Other home computer models of the 1980s included hardware support for digital sound playback or music synthesis (or both), leaving the IBM PC at a disadvantage when it came to multimedia applications.

It is important to note that the initial design and marketing focus of sound cards for the IBM PC platform were not geared towrads the gamers market, but rather on specific audio applications such as AdLib Personal Music System, Creative Music System, IBM Music Feature Card or on speech synthesis programs like Digispeech DS201, Covox Speech Thing and Street Electronics Echo. It took the involvement of Sierra and other game companies in 1988 to switch the focus toward gaming.