width work somewhat differently in CSS.
height looks "down" the tree
width looks "up" the tree.
heighttends to look "down" the tree, to determine its size based on the natural size of its contents, while
widthtends to look "up" the tree, basing its size on the space made available by the parent.
I don't know if the quote makes sense on its own (without more context).
But I thought it describes the difference between
very clearly yet succinctly,
so I wanted to share it here.