Server Side Includes (SSI) is a basic server-side language, which allows you to incorporate text from a specific source within a website. In the most common scenario, the text from a file is incorporated in a different one, providing a website the feeling that it's dynamic. As an example, if your site is made of 10 web pages, five of them can easily contain the content of some file, for example horoscope.txt. In case you alter this text file, the modified content will appear on all of the five web pages, which shall help you revise your website much easier than if you had to update part of all five web pages. Server Side Includes is sometimes employed to incorporate the output of basic commands, scripts or functions as well - a hit counter that is displayed on the website, the current date and time or the customer's IP address. Any web page that works by using SSI will need to have a particular extension - .shtml.