Section II provides background: some history of how the relation E=mc2 arose, what the word “mass” means in the context of that equation, and some aspects of how the relation
can be understood. In Sec. III, I refine the question in the title as “Does the equation E=mc2 mean that we can 'convert mass into energy’ and vice versa?” and provide a response.
Section IV summarizes the paper with a list of six key ideas.