minidisc is just the same as cd only smaller. the format allows for re writing to the disc many many times over. in addition it allows for editing, re-positioning and titling of individual music tracks. i have used it for about ten years now, it just aint caught on for pre recorded tracks.
Just like a normal re-writeable CD but smaller and convenient.
The reason they have not taken off is because they are expensive to make, compared to CD's.
If they could make them cheap they would be used in computers instead of CDroms.