flex-flow in CSS – How to Orient and Wrap Flex Children

flex-flow is a shorthand for the flex-direction and flex-wrap properties.

In other words, instead of writing:

section {
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
}

You can alternatively use the flex-flow property to shorten your code like so:

section {
  display: flex;
  flex-flow: column wrap;
}