Responsive in web designing means how your website will response in different screen devices. This feature will allow you see how your site will look on desktop screen, tablet screen, and mobile screen.
On the main settings of toolbar, you’ll find 3 device icons - Desktop, Tablet, and Mobile. Clicking on them will show you the preview of your site in the screens of desktop, tablet and mobile.
The column will response according to the device screen. In desktop mode, you can set three to five columns in a row. In tablet screen, the number of column in one row will be reduced to maximum three. And in mobile mode, each of the column will set one after another. But you can change these option and set your own.