What is the difference between a post and a comment on Reddit?

A post and a comment are the two fundamental types of user-generated content on Reddit, and they differ in their purpose, their placement, their editing capabilities, and how karma is counted from each. A post, also called a submission, is the initiating act of content creation within a subreddit. It has a title, which the poster must write and which cannot be edited after submission. Posts can take one of several forms: a link post (pointing to external content), an image or video post (uploaded directly to Reddit), or a text post (also called a self-post, containing the poster's own written content). A post lives at the top of a thread and defines the discussion that follows. It earns or loses post karma based on the community's upvotes and downvotes. A comment is a response — it exists only in relation to a post or to another comment. Comments can be written in response to the post itself (top-level comments), or as replies to other comments (nested replies). Unlike a post's title, the body text of a comment can be edited at any time after submission, though Reddit records an asterisk to indicate a comment has been edited. Comments accumulate comment karma, which is tracked separately from post karma on a user's profile. From a practical standpoint, posts require more deliberate effort and planning: they must comply with the subreddit's specific submission rules, they require a compelling title, and they tend to carry more reputational risk since a poorly received post is visible to the entire community. Comments are lower-stakes, quicker interactions that form the conversational texture of the platform. Most users engage far more through commenting than through posting, especially early in their Reddit experience.