Server Side Includes (SSI) is a basic server-side language, which enables you to incorporate text from a specified source inside a website. In the most typical scenario, the text from a single file is included in a different one, providing a site the sense that it is dynamic. For instance, in case your site comprises of 10 web pages, 5 of them can easily have the content of some file, like horoscope.txt. As soon as you change this text file, the updated content will come up on all five pages, which will let you revise your site much easier than if you had to update a component of all 5 web pages. Server Side Includes is sometimes employed to contain the output of basic commands, scripts or functions as well - a hit counter that's displayed on the website, the current time and date or the customer's IP address. Every webpage that works by using SSI will need to have a unique extension - .shtml.