system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What a circlejerk is and why it's bad.
gpt
Let's say your class had a debate on which was better, kitties or puppies. Maybe not even a debate. Maybe even just a show of hands.

And let's pretend that puppies won.

People might start noticing that puppies were popular, and that a good way to get attention or approval would be to enjoy puppies. Wearing t-shirts with a puppy on it to get compliments, for instance. Over time, the classroom might seem like home to an unofficial, unspoken Puppy Club, where the more you agreed with the Puppy Club the more accepted you were.

Here are some common games the Puppy Club might play:

— Make it sound like liking puppies was something new, or special, or unique, or even the oppressed minority opinion… you know, sitting down at a table where it was well-known that all the kids liked puppies, and saying, "Does anyone else think puppies are great and kitties aren't?"

— Bringing up puppies even when no one was talking about pets at all, just to get some cheap approval.

— Purposely making people who preferred kitties sound bad, or stupid, or crazy, or brainwashed; purposely turning pet conversations into puppies-versus-kitties talk, with no regard for birds or fish or turtles.

— Congratulating each other on how brave and special and smart they were to like puppies. Telling each other over and over again that their Puppy Club was how it ought to be and everyone else was making school a worse place. They would say this in places the Puppy Club had already staked out, of course, so they could say all that stuff without anyone challenging them.

— Making sure during class discussions that people praising puppies got a lot of attention and applause, and that people praising kitties didn't get to talk as much. (Grownups call this upvotes and downvotes: kids, ask your parents!)

— Shouting "Woof!" or "Roll over!" or a puppy-related catchphrase to win people's approval, while someone else is trying to give a worthwhile presentation to the class. (Whether it was even about puppies, or pets, or something different at all.)

All in all, the discussion would just start skewing toward what people would think would make the Puppy Club happy, with the result that no one really learns about other points of view, or even (sometimes) gets a full understanding of puppies.

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We call it a circlejerk because of something adults like to do. You could think of it as circle-gold-stars. Do you like to get gold stars on your work at school? Well, imagine if everyone sat in a circle with a sheet of gold stars and gave gold stars to the person on their right. It wouldn't really be the same as getting gold stars from the teacher, 'cause they just made this little circle to make each other feel good, but it would still feel good.

It's okay to feel good when your friends give you a gold star. But it's much better to have different opinions, that make good points about puppies and kitties, than about who comes away feeding the circle-gold-star mentality the most. That way we all learn something!