bundle products questions

Hi,
I already checked the documentation … but couldn’t really find an answer to my doubts.

1) what’s the difference between a “bundle” product and a collection of files of a “default product”?
2) is there a way to download a bundle product as a zip files? When we have for example 5 mp3 and not have to download each single one?
3) is there a way to import (with the import tool) a product as a bundle?

thank you!