What Edwyn says is true. That will get you low resolution MP3 copies of all your songs (128kbps, I believe). It will also convert all your WAV files to FLAC format. FLAC files have all the resolution of WAV files, but they take up less space. When the B2 converts to FLAC, all the converted WAV files are deleted. If you truly want to keep your files in WAV format, do not enable compression. But I agree with Edwyn, FLAC + MP3 is the easy way to go, so long as you don't mind your MP3 files in that low bitrate.
Here's what I do: I convert all my song files to FLAC - I don't save WAV files anymore (I did for a long time). When I want MP3 copies, I convert them on my computer to a higher bitrate, 256 or 320.