A password-protected directory is a folder which cannot be accessed unless the proper login details are offered. This can be a whole website or simply a single page that's located within a subfolder. If you attempt to open this type of a directory, you'll see a web browser pop-up where you must input a username and a password. If you input the appropriate ones, you will be able to continue browsing the content without having to do anything extra. When the login details are not correct, however, you will see information that you aren't authorized to look at the content. If this option is activated, you will not be able to open a file even if you have a direct link. The feature is incredibly practical if you'd like to prohibit the access to some content or if you are creating a site and you do not want visitors to be able to access it before it is ready.