As per Google’s new algorithm change on 21st April 2015, nicknamed Mobilegeddon, if your website is not mobile friendly, your search results will be severely affected. Google will rank you higher if your website is mobile friendly, or responsive. A recent study from Google shows over 50% of searches are now done from mobile devices, and visitors expect to see a mobile friendly site.
A Responsive Website re-sizes your desktop website for mobiles of any screen resolution. Google recommends Responsive Design as best practice for mobile-optimised websites.