WMA file is an audio file compressed with Windows Media compression. It is a proprietary format developed by Microsoft and similar to the MP3 format. WMA file can be converted to other more standardized formats. It is often used for playing music from the Web.
Windows Media Audio is also known as WMA Standard. Microsoft created it to compete against MP3, that was quickly becoming the de-facto standard format for lossy compression.
WMA is a file format based in ASF (Advanced Systems Format) that wraps an audio bitstream. It is usually a final state format for enduser delivery. Sometimes, it is also a middle-state format, e.g., a high-quality audio representation for archiving or as a source when producing lower-resolution streaming versions.