>
> So, what is the difference between these various formats


Compression, quality, and licensing.  Your needs may vary depending on
devices, space, etc.

and how can I convert the .wav file to an .mp3?


Install  "LAME" from whatever package manager Mandriva uses.  Then:
lame -m j -h --vbr-new -b 160 songname.wav -o songname.mp3

That creates a variable bit rate (vbr) mp3 @ 160 bps.
*note: some players are unable to play vbr mp3's.

also 'man lame' after you get it installed.