As the older music format, WAV was meant to play short sounds on any audio computer, it has been the primary format for sounds of the Windows. WAV files are found on the Web, and almost every browser has it's own WAV sounds. Although frequently used, WAV file formats are quite simple and basic. Bulky, but simple; any computer can play them, and they sound fine.
MP3 stands for MPEG-1 Audio Layer 3. The MPEG process compresses a sound sequence into a very small file, while retaining its original quality. The format compresses the file to approximately 1/12 the size of the original file, making it quicker to download or share with a friend. MP3 files are small and have their quality, and they are much more frequently used.
Though they both sound fine, the differences between the two file formats are quite profound. WAVs are much bulkier than MP3s, but require no additional software to play. MP3s require special players such as Napster or WinAmp. MP3s are better suited for swapping songs over the Web, while WAVs work better for audio-enhanced web sites.
Anyway, the WAV formats are not so good in quality, but frequently used for small durations of sounds. MP3 formats, with their lesser size and better quality, are used to sprinkle themselves over the internet faster.
I hope this helped you.