You earn karma when someone likes your post or comment. It feels good to have your opinion validated by others. Each upvote you earn is another person agreeing with you. However, karma can be earned, and karma can be taken away. This is where the hive mind comes back into play. Downvotes are essentially a punishment for having an opinion that differs from the hive mind's opinion. It's why you frequently see new users complaining about being consistently downvoted almost as soon as they comment or post. They haven't had time to learn what the "correct" opinions are, so they never earn karma. But over time they learn what earns them downvotes, what earns them upvotes, and they shift their opinions to match the opinions of other redditors."