Every single element on a page is a rectangular box. The sizing, positioning, and behavior of these boxes can all be controlled via CSS. By behavior, I mean how the box handles it when the content inside and around it changes. For example, if you donâ€™t set the height of a box, the height of that box will grow as large as it needs to be to accommodate the content. But what happens when you do set a specific height or width on a box, and the content inside cannot fit? That is where the CSS overflow property comes in, allowing you to specify how you would like that handled.