Server Side Includes (SSI) is a simple server-side language, which allows you to incorporate text from a specified source in a website. In the most typical situation, the text from a single file is included in a different one, providing a website the feeling it is dynamic. As an example, if your website is made of ten pages, five of them can include the content of some file, for example horoscope.txt. If you ever alter this text file, the updated content is going to appear on all five webpages, which will allow you to revise your site much easier than if you had to update part of all five web pages. Server Side Includes is at times used to include the output of basic commands, scripts or functions as well - a hit counter that's shown on the website, the current time and date or the customer's IP address. Every web page that utilizes SSI should have a particular extension - .shtml.