A favicon is a little icon visible on the web browser tab, just before the page title. It is generally a logo with a smaller size. The size of a favicon is 16x16, since it also gets displayed next to the URL of your site in a browser's address bar.
The 16x16 size for Favicon is suitable for web browsers. But the size varies on multiple platforms and devices. The size is added using the sizes attribute.
The preferred size,
Here’s how you can add them to your website,