The "classes" program is a Chrome Devtools add-on developed by Sandip Chitale. It is a useful tool for web developers who work with HTML and CSS. This add-on enhances the functionality of the Elements side panel in Chrome Devtools by providing additional information about classList and unique classes.

With the "classes" add-on, web developers can easily view the classList of any selected element in the Elements tab. This allows them to quickly see all the classes applied to an element and make necessary changes or modifications.

Furthermore, the add-on also displays the occurrence count of each unique class in the web page. This information can be invaluable when debugging or optimizing CSS code. The add-on even provides a usage count, which shows how many elements are using a particular class.

To select an element in the Elements tab, simply click on the icon provided by the "classes" add-on. This makes it incredibly convenient to navigate and inspect the HTML and CSS of a web page.

Overall, the "classes" add-on for Chrome Devtools is a must-have tool for web developers who want to efficiently analyze and manipulate classList and unique classes in their projects.