Flexbox and CSS Grid
The most popular CSS layout modules in recent years are Flexbox and CSS Grid.
Both layout modules support content placement in 2 dimensions … one of the main reasons to use one instead of the other is content placement vs content flow.
If you want to accurately control the position of items within a layout, CSS Grid is the way to go.
Flexbox enables you to allocate space and align items flexibly (determined by the item content).