The WAV file format has been around since 1991. IBM and Microsoft wanted to define a format for sound files, and it had to work with the slow processors and limited memory of the time. Compression could have made files smaller, but it would have put a major computing burden on the processor. With WAV, each sample is encoded directly as its bit value. It isn't efficient, but the original intent was to use the format for sound effects of a second or two, not for symphonies.
While it's primitive compared with other audio file formats, its simplicity has earned it a niche as an archival and editing format.
The format is a special case of RIFF (Resource Interchange File Format), a general-purpose format for packaging data and metadata. A RIFF file consists of "chunks," each of which has a four-character type. A chunk holds a particular kind of information, such as encoded audio, timestamps, and encoding parameters.
The format is similar to AIFF, an early Apple audio encoding format. Both use a similar chunk structure, but they aren't compatible with each other.
In Windows 2000, Microsoft introduced Wave Format Extensible. It provides better support for multichannel audio, including information on the positioning of speakers.
No formal standard has ever been published for WAV. Microsoft's definition is mostly in terms of an API. It has some ambiguities. The publicly available information is sufficient to create and play normal WAV files, and no license is needed. Some codecs may require proprietary information and licensing, though.