Server Side Includes (SSI) is a basic server-side language, which lets you incorporate text from a specified source within a website. In the most common situation, the text from one file is incorporated in a different one, giving a website the feeling that it's dynamic. For example, in case your website includes ten pages, five of them can contain the content of some file, for example horoscope.txt. Any time you modify this text file, the new content will come up on all five webpages, which will let you revise your website faster and easier than if you had to update an element of all five 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 displayed on the website, the current time and date or the customer's IP address. Every web page that utilizes SSI will need to have a particular extension - .shtml.