WAV format is the standard Windows audio file format and it was originally jointly developed by Microsoft and IBM.
Format itself doesn't specify any particular audio compression scheme, but actually supports several compression types. However, the most commonly used -- and the one people typically refer as ".wav file" -- is the one that uses IMA/ADPCM compression at 4:1 compression level for 16-bit sounds.
The format conforms to so-called RIFF specifications, just like several other formats do as well. However, due various historical reasons, the term RIFF-WAV has spawned its own meaning already, even though it really refers to just a regular WAV file, not a WAV file using particular compression scheme.
Windows operating system uses .wav files extensively for its audio operations, such as notify sounds, etc. Also, virtually all CD rippers use "raw" (the above-mentioned IMA/ADPCM compression) WAV format as their default method for outputting extracted CD audio tracks to file format.
Due its de facto standard status, virtually all Windows-based audio and video applications can use and play WAV files.