Reddit karma is Reddit's own voting system introduced to encourage active users to discuss, upvote relevant posts and useful comments while downvoting those that are not. Similar to a "badge of honor", the Reddit "karma" points mechanism has the following advantages:
Ensures the best possible content is shown in every search results list.
Prevents spammers from bombarding the readers.
Is an excellent tool for community building, retention, and engagement.
As people upvote or downvote a redditor's constructive contributions, these points add up to that user's "karma", which is made of:
"Comment karma" with points earned for comments on existing posts.
"Post karma" with points gained when submitting helpful external links or creating a text-only post.