What is external Style Sheet?

An external type of style sheet is a separate file apart from the HTML file(s). The external style sheet is given a .css extension. It is associated to the HTML document using a link element or an @ import directive in the head of the html document. Any html document associated to an external style sheet gets the styles, and that is where the maintenance power of CSS is found. Not only do external style sheets allow reuse of rules within one specific document. They allow the style sheet itself to be shared across multiple documents. Using external CSS allows you to maintain a single style sheet for an entire site.