As of the 21st April, 2015, the Google search engine, globally, is giving weight to the presence or absence of mobile responsiveness in your website for people searching in Google using a mobile device. For example, if you are searching for a local cafe while using your mobile phone, the local cafe that has a website which is optimised for viewing on a mobile phone is much more likely to appear in the top search results for your Google search.
Google have been warning about this change for some time, so if you don’t have a mobile responsive website yet and if people searching for your business are likely to do that using a mobile device (tablet, phone, mini-tablet etc), now is definitely the time to act.
In a nutshell, a mobile responsive website is one that lays out differently and potentially functions differently, depending on the size of the screen being used, and whether the device has a touch screen or not.
Below is an example of a website which has been built responsively (the Contact Point website):
You can read more about what it means to have a mobile responsive website here.