Are "discussion"and "post"the same concept?

My explanation is that everything here is a 'post' but for clarity we break it down into 3 types of posts: A discussion, which is the original post that started it all. A response, which is the post other people make in response to the discussion. A comment, which are all the posts that are in direct reply to a response made under a discussion.

A discussion is the the actual thread that is actually being created then others post cemments in that discussion, well thats the way I look at it...