VBR (Variable Bitrates) basically makes the tunes as good as a quality as they need to be.
Imagine this,
You've got a couple of boxes, ones labelled 320K and one labelled 160K. Some tunes wont fit into the 160K box because the depth of the files are too large, and they can't compress enough without reducing the quality a lot. These boxes are fixed values and called Constant Bit Rate (CBR).
This box represents CBR, no matter what sort of shit you put inside it, it will always be a 320K box.
VBR (Variable Bitrates) are basically what is known as shrink wrapping. Your stuff is placed inside a 320K MP3 box and then the lid is sealed and all the excess (air in this case) is removed. So in an ideal world you can have a smaller file size with the same quality.
Remember MP3's run on the same sort of technology as your .ZIP and .RAR files - compressing them. WAV's are uncompressed.
Some programs will always trim the edges though and well, you can't be too sure you're definately getting everything with an where a WAV will have everything you need, and everything you don't need too.
I hope thats understandable?
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