This affects searches done from mobile devices only. Desktop search results will not be affected.
This could be bad news for 40% of the top websites that are not mobile friendly, causing them to rank lower in search results.
You can test a website to see if a website is mobile-friendly with this Google test site: https://www.google.com/webmasters/tools/mobile-friendly/
Google also gives priority to pages that load fast. Building a mobile friendly website that loads fast is a must for businesses to be competitive. Contact us, the mobile web experts, to find out how you can improve your website to be mobile-friendly and fast.