Mobile Responsive Websites are basically mobile-friendly sites which are designed in a way to provide the best user experience for mobile users.
Why is it important?
There are more than 4 billion mobile users and it is proved that a website is mostly accessed by a mobile device instead of a desktop or laptop. If you ever contact a  hire dedicated resources company then make sure that their developers are more concern about the user interface of the mobile structure. A smooth mobile website is an utmost step in website development.