What is the different between filter and segment?

[smmexpertss]

I was wondering why there's a difference when I use the advanced segment and filter advanced page on page.

For example, on my advanced segment:
page= doent match a regular expression = ^/$
Results=many pages with 3,675 pageviews total

and on my advanced filter on page:
Filter page=exclude =^/$
results=many pages, with pageviews:55,393 total

why this situation?
there's something wrong on my test??the data should not be the same??
thanks a lot