flex is a new value added to the CSS
display property. Along with
inline-flex it causes the element that it applies to in order to become a flex container, and the element's children to each become a flex item. The items then participate in flex layout, and all of the properties defined in the CSS Flexible Box Layout Module may be applied.
flex property is a shorthand for the flexbox properties
<flex> can refer to a flexible length in CSS Grid Layout.
- CSS Flexible Box Layout Module Level 1 Specification
- CSS Flexbox Guide: