Quetree members with a username can freely join public communities. This type of communities have the widest reach.

Membership can be restricted in several ways while non members can still view and vote on the questions and answers.
Best for when you want to share the knowledge and understanding with a wider audience but want to keep the Q&A growth to members only. e.g. a technical research lab.

Membership can be restricted in several ways and non members cannot view anything.
Best for when the knowledge is only relevant and personal to your group e.g. your family.

A context is something that raises questions. It can be anything like a story, an event, a talk, a theory, a youtube video, etc. You can add multiple questions to a context.

This is the base structure and is the only structure supported by other Q&A sites. Answers to a question are rated by users and the more highly rated answers rise to the top.

Followup questions to answers can be raised for better understanding. An answers that gives new knowledge and understanding can lead to the discovery of even more important questions.

Recall the common reply to a question: "it depends". You can raise "depends on" questions to a question to either break down to simpler ones or to ask preliminary questions that need to be answered before answering the original question.