To view the results of a segment head to "Segmentation", then find your segment in the list. Once you have found the desired segment click "View More".
Once on the results page, you will notice a chart representing the subscribers by date, along with a list of the subscribers in that segment which can be exported to a CSV document.
You'll also be able to view which campaigns the segment has been used in by clicking "Segment Locator".
Once on the Segment Locator tab, you will see a list of campaigns that have used the segment along with the campaign type, ID, status, and sent date.