Here you'll find a brief description of what audiogames are, how they work, and some links to popular audiogaming sites.
Audiogames are games played by the use of sound and/or text. An audiogame is usually made up of just sound and synthesized or recorded speech, meaning that you don't have to see to play them. Some audiogames require headphones for best sound experience, others may not; it all depends on the nature of the game in question (an FPS versus card games, for example).
Audiogames can be found on most operating systems, including Windows, Mac, Linux and mobile devices. Some audiogames require the use of a keyboard, whilst others can make use of the mouse. A few offer joystick support. While it is true that most audiogames require the use of headphones in order to play the game to the fullest, not all games require this. You'll usually know when a game requires a pair of headphones or a set of stereo speakers by an announcement that this is required. Some audiogames also include the use of graphical content. This is rare especially among older games, but becoming more and more popular as time progresses and the line between "video" and "audio" games blurs.
Here is a list of sites that audiogamers may frequently visit to discuss audiogames, provide resources and plan out new development.