Server Side Includes (SSI) is a simple server-side language, which allows you to include text from a specific source inside a website. In the most typical case, the text from a file is incorporated in another, giving a site the feeling that it's dynamic. For example, in case your website is comprised of ten webpages, five of them can easily have the content of some file, for example horoscope.txt. As soon as you modify this text file, the modified content is going to appear on all five pages, which shall enable you to revise your site faster and easier than if you had to change a component of all 5 web pages. Server Side Includes is sometimes employed to incorporate the output of simple commands, scripts or functions as well - a hit counter that is shown on the website, the present date and time or the customer's IP address. Any web page that uses SSI must have a special extension - .shtml.