relating to the process of asking a question and answering it yourself - either immediately via the 'Ask Question' page or from finding out the answer yourself later.
A 'Self-Answer' is when the question asker answers their own question. This is not only allowed, but encouraged: other people may benefit from your knowledge.
There are two main ways to post a 'Self-answer':
Via the 'Ask Question' page
By clicking the 'answer your question' checkbox you can provide an answer along with your question. When you click 'Post your question and answer', both go live immediately.
Posting an answer later
You may continue to research or test, and find your answer yourself. You can then visit your question and post an answer normally, like any other question.