A responsive website is a modern website whose layout automatically adjusts to the screen size of the device on which it is displayed. The content displayed on the screen scales so that it is comfortable to view for any user, on any device
As of 2018, the Google search engine officially favors responsive websites, so any online stores and websites that are based on modern, responsive architecture will be displayed in higher positions. This means that outdated sites have to reckon with a steadily decreasing position in google, and thus a lower number of visits from potential customers.