Privacy Badger inspects the target domain and then pulls out requests to 3rd party domains. If you go to cnn.com and it makes additional request from your browser for resources at say facebook.com. Those 3rd party requests can be allowed, block cookies from the 3rd party or blocked entirely (so the request is not made). The really nice bit, is if Privacy Badger see's requests to the same 3rd party across multiple places, it'll filter it down automatically.