Flexbox is a nickname for CSS Flexible Box Layout Module. It’s one of a few CSS Working Drafts having to do with visual layout. Flexbox offers us a new box model which has been optimized for laying out user interfaces. In short: the children of a “box” can be ordered either vertically or horizontally within their parent, and we can control what happens to any remaining space. It is possible to nest these boxes, allowing for very complex layouts.