Every DV AVI file has a wrapper, think of it a a book wrapped in gift paper. If you go to store A, you get a wrapper indicating store A, but if you got the same book at store B, the wrapper indicates store B as the source. The book inside the wrapper is exactly the same. The wrappers used for DV AVI files are very much similar. What the program does is exchanging the paper wrapper from store A and replacing it with a wrapper from store B, but leaving the same book inside. Nothing is changed in the contents, but the packaging is adjusted to the flavor the NLE likes better.
Another analogy, buy your wife/partner/girlfriend a purse. Would she prefer you coming in with this gift to come from Marks & Spencer, Harrods or Gucci? That is the wrapper.
The program allows you to batch convert from wrapper A to B.
Hope this explains it somewhat.
Harm Millaard