CSS Layout is all about boxes. We know that some boxes are blocks, and others are inline, and we can change the display type of elements by changing the value of the display property. That property holds the key to much more than this, however. It is the foundation on which all layout is built; the core of the inbuilt CSS layout system. Learning Grid Layout, or Flexbox, without understanding Display, leaves you with a wobbly foundation and more questions than answers.
The real question isn’t “Should I use Grid or Flexbox?” but instead, “How do I want these boxes to behave?” Understanding the interaction between layout methods will enable you to easily create fallbacks for older browsers, and knowing how the various formatting contexts behave unlocks margin collapsing and the behavior of items inside grid or flex layout. By the end of the hour, you’ll understand how the display property underpins the layout system we have today, the things coming in the future, and be able to make more informed decisions when deciding how to build any part of your design, big or small.