The difference is a sequence of commits that implement a feature where each commit basically is a logical change that does a single thing (e.g., add a function and associated test, add calls to a new function, etc) versus a sequence of commits with additional commits that fix issues brought up during review. Those additional commits really should be amended to the corresponding original commit rather than being a completely separate commit.

Another way to look at it is submitting an assignment where you have one page per problem solution as opposed to submitting that and then several more pages at the end containing fixes to those problem solutions rather than incorporating those fixes in the original set of pages.