A password-protected directory is a folder that cannot be accessed unless the right login credentials are offered. This could be an entire site or simply a single page that is situated in a subfolder. If you try to open this type of a directory, you shall see a browser pop-up in which you will have to type a username and also a password. If you input the appropriate ones, you will be able to continue browsing the content without having to do anything additional. In case the login credentials aren't accurate, however, you'll see information that you aren't permitted to see the content. In case this feature is active, you won't be able to open a file even though you may have a direct link. The feature is quite useful if you want to prohibit the access to some content or if you work on a site and you don't want visitors to be able to access it prior to it being ready.