Server Side Includes (SSI) is a simple server-side language, which lets you include text from a specific source in a website. In the most widespread case, the text from a single file is incorporated in another, providing a website the sense it is dynamic. As an example, if your website involves 10 web pages, five of them can easily have the content of any kind of file, like horoscope.txt. Once you alter this text file, the modified content will come up on all five pages, which will let you update your site much easier than if you had to change an element of all 5 pages. Server Side Includes is sometimes used to incorporate the output of basic commands, scripts or functions as well - a hit counter that is displayed on the website, the present date and time or the customer's IP address. Any webpage that works by using SSI should have a particular extension - .shtml.