You've been hearing for some time that you need to have a Responsive Website (one that automatically reconfigures to the device from which you are viewing, whether desktop, tablet or smart phone).
You may also have heard that Google penalizes websites that are not responsive by making them appear lower on the search results page when one searches on a mobile device.
What you may not have heard is that Google recently announced it has started experiments to make their indexing "mobile-first." Thus, Google algorithms will eventually, primarily, use the mobile version of a site’s content to rank pages.
What the new algorithm will mean to you:
Your site’s mobile experience will be the primary point of reference when your content is indexed, not your desktop pages (which is the case currently). If you already have a responsive site and have not reduced the amount of content to better fit the mobile form factor, then you have nothing to be concerned about.