Reddit glossary
What is Subreddit rules on Reddit?
Subreddit rules are the written dos and don'ts of a community, usually shown in the sidebar or the About section.
Rules cover things like what kind of posts are allowed, whether links are okay, and whether you can mention your own product.
They are only part of the picture. Each community also has habits that are never written down. You learn those by reading what gets upvoted and what gets removed.
If you are promoting something
Read the rules before you write a single word, and again every few weeks. Rules change, and not knowing them is never accepted as an excuse.