Web, domains and email
ICO
Abbreviation for icon
In short and in plain language
ICO is a format for small pictures. Such pictures are called icons.
A file in this format can hold the same icon in several sizes.
Websites often use it for the small picture next to their name. You see it in the browser, for example.
Definition
ICO is a file format for small icon images. An ICO file can contain the same icon in several sizes. Websites often use the format for their favicon, which browsers and search engines can show next to the name of the website.