If your website is not mobile friendly it may stop appearing on searches made on mobile devices. That is according to the new rules set by Google last week.
As policies go it does make sense. Why show results which are difficult to view on the device you're searching on? The question was is your website mobile friendly? If you don't know and you're on a desktop computer. First set your windows to 'Cascade' so you can see more than one window at a time on your desktop. Then using the bottom right hand corner of the browser window drag to width of the window in. If the website is responsive or mobile friendly the layout of the page will adjust to the width of the window. In some cases you might need to refresh the page but that is normal.
What Google is looking for when being Mobile friendly is that a user doesn't need to scroll sideways to view content. Text is legible i.e. big enough to read on the device you're using. Links can be selected individually and that they are not too close together. There's more of course but those are the main issues.
If you want a more thorough check of your website use Google Mobile Test.
If it fails you know where to come.