When you like or comment on something on Facebook, you’ll get notifications when others comment on it as well; Facebook wants to keep you in the loop in case it’s a conversation you care about.
But if that post gets popular and the conversation blows up, or maybe you’re simply not interested in it anymore, you can stop these notifications. If you’re on a Mac or PC and the post is in your News Feed, click the carrot menu in the upper right and choose “Stop Notifications.” If it’s something like a photo that opens in a lightbox viewer, a “Stop Notifications” option appears among the “Like, Comment, Share” links.
If you’re on a mobile device, a carrot menu at the top right of the post also has a “Stop Notifications” link.