If a background-image is specified, the background-attachment CSS property determines whether that image's position is fixed within the viewport, or scrolls along with its containing block.
This keyword means that the background image will not scroll with its containing element, but will scroll when the element's content scrolls: it is fixed regarding the element's content.
This keyword means that the background image will not scroll with its containing element, but will scroll when the element's content scrolls: it is fixed regarding the element's content.