A few times I've been asked what it means on Flickr when one of your photos is "explored". It seems that more recently, Flickr emails you to tell you your photo has been explored. That means that it is one of the photos picked that day to go onto pages of "interesting" photos. Photos that are explored tend to be those that have had a rush of interest when they're first posted so when you're in a busy swap or when you add your photo to several Flickr groups, it seems to have more chance of being explored than if you just drop it quietly into your photostream.
If you go to bighugelabs scout, you can enter your Flickr name and your explored photos will show up. Click on "include dropped" and more will appear. Click on "create a scout poster from these images" and you will end up with one of these posters which you can add to your Flickr photostream or store away on your blog for future reference. It's just a bit of fun really and a chance to take a little moment to pat yourself on the back, which I'm never averse to.