The breakpoint group typically only needs a single breakpoint with an empty media query in order to do <em>viewport sizing.</em> Multiple breakpoints are used for changing the crop or aspect ratio of images at different viewport sizes, which is often referred to as <em>art direction.</em> Once you select a breakpoint group, you can choose which breakpoints to use for the responsive image style. By default, the option <em>do not use this breakpoint</em> is selected for each breakpoint. See the <a href=":breakpoint_help">help page of the Breakpoint module</a> for more information.