Semantic HTML: Usage of Headings, Sections

Wondering how to layout and use <section>, <h1>, <h2>, etc. I came across the first place one should read on MDN Using HTML sections and outlines also very insightful and more specific is this on the W3C wiki HTML/Usage/Headings/Missing. If you have 27 minutes to learn how to use all those semantic tags watch Brian Haferkamp's Semantic Elements and Structure a very well explained video.