Glossary
What is a restricted area?
Airspace containing hazards to aircraft that are invisible from outside it, such as artillery fire, gunnery or guided missiles. Unlike a military operations area, entering an active one requires permission from the controlling agency, and going in without it is a violation.
That is the whole entry for now. The longer version, with the mechanics and worked examples, is still to be written. See autorotation for how those read once they exist.