Server Side Includes (SSI) is a basic server-side language, which allows you to include text from a given source in a web page. In the most popular scenario, the text from one file is incorporated in another, giving a site the sense that it is dynamic. For instance, in case your site involves 10 web pages, 5 of them can include the content of some file, like horoscope.txt. If you alter this text file, the modified content is going to appear on all of the five webpages, which shall allow you to revise your website faster and easier than if you had to modify part of all 5 web pages. Server Side Includes is occasionally utilized to contain the output of basic commands, scripts or functions as well - a hit counter that's shown on the site, the current date and time or the customer's IP address. Every webpage that works by using SSI will need to have a particular extension - .shtml.