Yes. If you've created a subdirectory without an index.html file in it, you'll simply see a list of the files it contains when you visit that subdirectory's web address. If you add an index.html file to your subdirectory, visitors to your subdirectory won't be able to view the list of all the files in that folder; instead they'll see the contents of your index.html page. This index.html file works exactly like the index.html file in your main directory (your home page).