On an Internet browser, what is a favicon?

What’s the Difference Between a Favicon and an Icon?
An icon can represent any application or function and might appear in various sizes across different platforms. A favicon is specifically designed for use in web browsers and is usually small (16x16 to 64x64 pixels).

Logo vs. Favicon: What’s the Difference?
A logo is a full-sized design used prominently for branding, visible on products, marketing materials, and websites. A favicon is essentially a miniaturized icon derived from the logo or designed separately to be recognized at a much smaller size.