Discussions
A discussion is a thread: someone starts it, and other people reply. On the site the thread is called a Topic and the conversation inside it a Discussion. Each answer is a Reply. Threads are filed under categories, and a thread can belong to a community.
Description
A post in a discussion is a markdown document like any other document you write, so it is searched, versioned and reacted to the same way. Search over discussions finds words anywhere in a thread.
Signed in, you can start a topic, reply to one, bookmark it and react to it. Anyone can read discussions without signing in, but not write to them.
Tech Detail