The majority of websites that we come across on the interwebs today are dynamic sites. What this means in simple terms is that all the elements you see before you — images, text, other assets — everything has been put together piece by piece when you hit enter after typing a URL or when you click on a button.
Websites, at the time, were a collection of these static documents, stored in their entirety and there was minimal interface on the server-side. With the introduction of CGI or Common Gateway Interface, this changed. CGI allowed websites to run scripts and this enabled the webserver to be more than just a storage facility of static