Josie. The free version is really just an audio player. It is what you are left with after your free trial is over. I used to use it to make midi files from a wave file but they removed that functionality. It was about that time I decided to buy it.
The full studio version is useful if you have multiple tracks that you want to line up with each other. The album with my old band mate Karen Wilmot "Alice band 20 years on" would have been a bit of a mess without it because I had her vocal and my vocal that where just never in time no matter how hard I tried and how long I practiced. With melodyne studio you can line everything up perfectly so that the plosives "p's" etc sound at the same time and the words start and end at the same time etc.
For me it is simply the best tool for manipulating audio.
Edited to add; I think in the "old" days you just had to spend hours and hours in the studio trying to line up vocal parts. Now with melodyne you don't have to do that (of course the vocal needs to be quite good to begin with otherwise the results will not be great). So you can get quite a good out come with relatively little effort and that, I am for
