A favicon is a small image that resides in your browser’s ‘tabs’, so you can identify the brand at a glance. Favicons may also display in bookmark lists too.
Here are examples, outlined in yellow, of favicons appearing in the browser:
You can see that it is common to use a smaller version of your logo for your favicon to keep consistency throughout your site and branding.
This is really easy to do. Just head to:
Online Store > Themes > Customize
5. Choose “Select image”