GitHub Discussions are where you can talk about things without opening issues.
Go to settings. Then scroll down to Features. There is a new item named "Discussions". Enable it.
Press "New Discussion". Then you can set the topic for the discussion (General, Ideas, Q&A, Show and tell. You also can make your own topics),the title for the discussion, and write a comment.
Now that your Discussion is set up you can write a comment. Below the comment there will be a "Reply" form, where someone can reply.
If someone has a Discussion with a topic of Q&A, and you know the answer you can write down the answer in the comment box. If the answer helped the person they can mark it as a answer.
If you have a Discussion with a topic of Q&A, and someone gives a answer that helps, press the checkmark on the comment to mark it as the answer
This is my first gist. I hope it is helpful.