Based on the statistics of how most of you get here (oh yes, I am watching you, my sweet) and from talking to the readers I know personally, I presume the majority of you aren’t familiar with Reddit or how it works. So, here’s a brief introduction.
Once a link is posted, the other users can choose if they want to upvote or downvote the link, or do nothing at all. This serves as a crowdsourcing of filtering and separating the content. The posts that get upvoted the most move higher up the list, culminating at the front page of the subreddit where the most popular posts reside.