Starting around April 21st, 2015, Google will start emphasizing websites that are mobile-friendly, and de-emphasizing websites that are not mobile friendly. The basic definition of mobile friendly is - can you easily navigate the website on a mobile device? Does it appear at a natural size, or do you have to "zoom in"?
See this article for more technical information: http://www.thesempost.com/googles-gary-illyes-qa-upcoming-mobile-ranking-signal-change/
SEO, as you may know, stands for Search Engine Optimization - it's the best practice of making sure your website follows guidelines so that it can naturally get a good rank on search engines, the primary one being Google. Ultimately, after all is said and done, the quality of content has more impact than any individual "SEO technique", but it's always a good idea to learn how to make a website that connects well to search engines.
So what's a website owner to do?
There's no "one" answer to making a website mobile friendly, but for many, switching to a "mobile friendly platform" can make sense. General information is easier to convert over to a mobile friendly platform than ecommerce, but nowadays there are more options for mobile friendly ecommerce too.
One popular platform for blogs and other kinds of websites is Wordpress, and you can find a mobile-friendly template that can help you get going in the right direction. There are also a new generation of free or low-cost "web site platforms" where you can create and manage a website entirely online, without having to use a program like Dreamweaver (the traditional way): Wix.com, Weebly.com are examples of these, very popular.
One platform I've been impressed with lately is Strikingly. It allows you to have an impressive looking, modern mobile-friendly website, and is very easy to use. I used it for creating the NPOEx site: http://npoex.com - try looking at the website on a laptop, and then on a mobile device.
Best wishes navigating the world of going mobile-friendly!
