You like how Flickr handles and displays your photo uploads, but far more friends are on Facebook than Flickr. A new integration between the two services makes it easy to have your photo geekery and share it too.
The gist of the integration is that, after you head over to Flickr and "extend" your account to Facebook, any photos you post with public viewing rights on Flickr will be cross-posted to your Facebook news feed. You'll want to make sure you've turned off Flickr and Facebook's older method of cross-posting, as described at ReadWriteWeb.
You can get a little more fine-tuned about what gets shared and how, but for most folks using both services, it's just a nice time saver in the default mode.