You get Reddit karma when people upvote your posts or comments. You lose karma when people downvote your posts or comments. Simple.So if you create helpful posts or you help people asking a question by giving them a really good answer, people will upvote your post or reply, which increases your karma score.Likewise, if you’re posting spammy rubbish everywhere, or leaving rude and unhelpful replies, your posts/replies will get downvoted.Some sub-reddits will have a minimum karma score before granting entry, as they want to keep the quality of the group high.Reddit also uses the karma score of a post as a way of working out the best content. If a post gets a lot of karma early on, it could make it into the ‘hot’ section, which is similar to ‘trending’ on Twitter or ‘top’ on Instagram. ‘Hot’ on Reddit can put you on the homepage, and help your post catch fire and go viral.