Server Side Includes (SSI) is a basic server-side language, which allows you to include text from a specific source in a web page. In the most widespread scenario, the text from a file is integrated in another, giving a site the feeling that it is dynamic. As an example, if your site has 10 webpages, five of them can contain the content of some file, for example horoscope.txt. Once you change this text file, the updated content will come up on all of the five webpages, which will let you update your site much easier than if you had to update an element of all five pages. Server Side Includes is in some cases used to include the output of basic commands, scripts or functions as well - a hit counter that's displayed on the website, the present time and date or the visitor's IP address. Any web page that works by using SSI should have a particular extension - .shtml.