The ‘Favicon’ has been around on the web so long that everyone knows what it is, even if they don’t know the name. It’s the small icon which appears in a web browser in various places, representing a particular website. For example, in Chrome it appears on the tab showing the web page title, and in both Chrome and Safari it appears next to the site or page name in the bookmarks lists.
Most websites have these, although they may have been set up years ago and might look a little stale and unloved. However, as with everything web-related, things move on, and there are reasons to re-visit what you’ve got. For example, although Favicons were originally only tiny, to appear in low-resolution address bars, nowadays they can appear quite large, in high-resolution (try making a page bookmark on your mobile phone and add it to the home screen as a shortcut).
The first thing to do is to check what you’ve got with one of the online tools, like this. Many people will discover that their desktop browser icon looks a little blurry, because they haven’t added larger sizes in recent years. Even more may find that their iOS and Android touch icons are missing completely. If so, your website designer should get on the case immediately (there’s a Favicon generator on the same site).