A quick and easy high level introduction to CSS Grid and its key concepts by Morten Rand-Hendriksen at Wordcamp Europe. Within eight minutes you'll understand what CSS Grid is and how to start making a basic layout of your own using CSS properties like grid-template-areas and grid-template-columns.
This has been adapted/edited from a CC-BY-licensed longer talk whose original is available at https://www.youtube.com/watch?v=txZq7Laz7_4