WMA stands for Windows Media Audio. A proprietary audio format owned by Microsoft, part of Microsoft's Windows Media technology.
Initially intended to combat the increasingly popular MP3 format, WMA was supposed to be Microsoft's answer to digital music. With the massive influx of constant bitrate, high quality, low file size MP3s flooding the Internet, it soon became clear to Microsoft that they would not be a direct competition for the format.
Thats not to say Microsoft didn't put their heart and soul into development of this audio format. Its configurable to be cbr, vbr and lossless audio encoding for a wide variety of options.
Encapsulated in an ASF container, WMA has one ability that seems to attract more and more businesses and allows this format to stick around. Thats the easy inclusion of DRM or Digital Rights Management directly into the WMA file. This ASF container also gives the WMA two file options. (.wma for strictly audio and .asf for features simliar to ID3 tags in MP3s)
Related software tools
Winamp Full (Freeware)
Nullsoft Winamp is a fast, flexible, high-fidelity media player for Windows.