Reddit glossary
What is Subreddit on Reddit?
A subreddit is a community on Reddit built around one topic, with its own rules and its own moderators.
Reddit is not one big feed. It is thousands of smaller communities, and each one is called a subreddit. You write them with r/ in front, like r/smallbusiness or r/fitness.
Every subreddit decides for itself what is allowed. Two communities about nearly the same thing can have very different rules, tone and tolerance for links. That is why a post that does well in one can get removed in the other.
If you are promoting something
Picking the right subreddits matters more than posting a lot. A few communities where your buyers already ask questions will do more for you than twenty random ones.