A mobile friendly website means that website is fully responsive to fit any type of device including mobile phones, tablets and desktops. The content on your website must be easily viewable and should not scroll across, meaning the viewport is set to fit the full width of the screen. Elements inside your website such as buttons should be easily accessible as well as all content being easily readable.
Ensuring that all webpages are mobile friendly is one of the most important factors when search engines evaluate your website. Having a mobile friendly website means you're more likely to be rewarded with a higher search engine results position.
If your not a web designer/developer, it may be worthwhile getting in touch with one. Or if you fancy a go yourself, you'll have to learn about media queries that allow you to display your content differently depending on what width, height or type of device is viewing your website.
Take a look at some more of our free SEO tools that are available.