Simple Wikipedia
When I want to understand dense subjects, I just visit Simple Wikipedia. All the entries are written in shorter sentences with easier words. The site is designed for children, adults with learning difficulties or for those trying to learn English, but for me it’s a great way to grasp complex topics, like how nuclear weapons are built and work. It doesn’t work with all pages, but sometimes replacing the “en” with “simple” in the URL will redirect to you the Simple English Wikipedia. — CD