Server Side Includes (SSI) is a basic server-side language, which allows you to include text from a specified source inside a web page. In the most common scenario, the text from one file is incorporated in a different one, giving a website the feeling it is dynamic. For example, in case your website comprises of ten web pages, 5 of them can contain the content of any kind of file, like horoscope.txt. If you ever change this text file, the new content is going to appear on all of the five web pages, which will let you bring up to date your site faster and easier than if you had to modify a component of all 5 pages. Server Side Includes is occasionally utilized to contain the output of simple commands, scripts or functions as well - a hit counter that's displayed on the website, the present date and time or the visitor's IP address. Any web page that employs SSI must have a unique extension - .shtml.