Server Side Includes (SSI) is a simple server-side language, which lets you incorporate text from a specified source in a website. In the most common scenario, the text from one file is incorporated in a different one, providing a website the sense that it is dynamic. As an example, in case your website is made of 10 web pages, five of them can have the content of some file, like horoscope.txt. Any time you change this text file, the new content will appear on all of the five pages, which will allow you to update your site faster and easier than if you had to update part of all 5 pages. Server Side Includes is at times used to include the output of basic 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 makes use of SSI will need to have a particular extension - .shtml.