I am fairly new to web development and I wanted to get an idea of the ever growing practice of hiding web page extensions. Most websites now show up as www.sitename.com/folder/ or www.sitename.com/folder/file in place of the traditional www.sitename/folder/index.html or php. how is that done? Do they create folders for each file? or using mod-rewrite functions of Apache? I searched around but what I found didn't seem all that standardized to me.