I don't get Explore. It's a section of Flickr where they highlight photos with the most "interestingness" every day. Think of the thousands and thousands of photos uploaded to Flickr every minute of each day -- 500 of those will make it into Explore for that particular day.

Interestingness is based on a behind-the-scenes formula that no one really knows, but it's somehow determined by the number of views that a photo gets, combined with the number of times it's marked as a favorite by other Flickr users and the number of comments the photo receives. Tags also come into play, as well as how many groups the photos is in. Again, I don't get it, but I have 23 photos in there, and I think it's kinda cool to unexpectedly find one there. Like I did with this balloon photo this week:

To see if you have photos with lots of interestingness according to Flickr and your fellow photographers there, visit the Big Huge Labs website. Their "Scout" feature will tell you.