The move has come about as a result of the change in people’s browsing habits and Google’s wish to provide relevant search results. Apparently more than 50% of websites are now viewed on mobile devices such as smartphones and tablets. If the websites have not been optimised for mobile devices then the user experience is likely to be disappointing with the need for horizontal scrolling, screen pinching, and links that are so close together that it is difficult to choose the right one.
There are other solutions but ideally you need to make your site design responsive. This means that you have one website design and the site’s style sheets (css) detect the device and format the information displayed accordingly.
If you are not sure whether your website is mobile freindly you can test it here:-
https://www.google.com/webmasters/tools/mobile-friendly/
If it fails you or your web designer need to fix it. If you need any help or advice, get in touch