When initially developing a website, you might want to restrict access to certain members of your development team. If your corporate website contains sensitive financial data, you might want to restrict your financial statements to a particular list of investors. Or maybe you just don't want people poking around in your personal things.
A common type of user authentication is database-driven, in which usernames and passwords are kept in a database table and accessed via a login form and script. In the next section, you create this database table and add some users to it.