Basically, it's software sound solution (as opposed to hardware sound solutions, such as a dedicated sound card) that is used mostly by developers as an alternative to low-end sound chipsets (like those found on motherboards with built in sound). It has very low CPU over head and provides good and robust sound for a software solution. Basically, it's great for those that don't have a dedicated sound card and have to rely on using the sound on their motherboard.
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