How to structure web pages

What's the technique behind when pages on a website is structured like this? http://ift.tt/2mW8bBG

When looking in the code behind it is obvious that page in question is actually placed in the root (domain.com) and furthermore it is possible append anything to the URL (like http://ift.tt/2nrou5V) and yet it still returns the correct page?

I simply don't know what to google for.