Web assets are elements such as CSS, JavaScript, Fonts, and image files that make the front-end which is the look and functionality of your website that is processed by the browser you are using (e.g. Google Chrome. Mozilla Firefox, Safari, Internet Explorer, Opera etc.). Asset CleanUp Pro deals with CSS and JavaScript assets which are enqueued in WordPress by your theme and other plugins and cleans up HTML code from the HEAD section of your website that is not needed.