Server Side Includes (SSI) is a basic server-side language, which allows you to incorporate text from a specified source within a website. In the most common scenario, the text from a file is incorporated in another, providing a site the sense it is dynamic. For instance, in case your site is comprised of ten pages, five of them can have the content of some file, for example horoscope.txt. If you ever change this text file, the updated content will come up on all of the five web pages, which shall help you bring up to date your site faster and easier than if you had to update a component of all 5 pages. Server Side Includes is in some cases employed to contain the output of basic commands, scripts or functions as well - a hit counter that's shown on the website, the current date and time or the customer's IP address. Every web page that makes use of SSI should have a special extension - .shtml.