According to the QA FAQ:
What is Microsoft Q&A?
Microsoft Q&A is a global, community-driven platform for timely, high-quality technical answers. Microsoft Q&A has replaced MSDN and TechNet forums for English users. Microsoft Q&A will replace MSDN and TechNet forums for non-English users in the future.
Why Microsoft Q&A?
We know how important it is for customers to have access to fast, accurate answers to questions about Microsoft technologies. However, MSDN and TechNet forums are outdated. Microsoft Q&A provides the set of capabilities that our customers need and want, and it is based on a robust, scalable, and reliable new platform and architecture.
What are the major benefits of Microsoft Q&A versus MSDN and TechNet forums?
Microsoft Q&A uses the same user authentication as Microsoft Learn and Learn content for a more consistent experience across the platform. This integrated experience allows us to better prioritize and answer questions, and give users clearer paths between documentation, learning content, and answers. Microsoft Q&A also offers a much better set of permissions that equips our moderators with improved tools to insure healthy engagement on the site.