Flex

Flex Layout Resource 1

This site provides an overview of the different flexbox properties and how they work.

Flex Layout Resource 2

This site is also an overview of the flexbox properties. It discusses writing direction and reordering flex items.

Flex Layout Resource 3

This site discusses the same flexbox properties.

Summary

These sites discuss various flexbox properties such as flex-grow, flex-shrink, flex-basis, flex-direction, flex-wrap, justify-content, and align-items.