The document discusses PHP and MySQL for building web applications. It begins with an introduction to PHP, explaining that PHP is a widely used server-side scripting language suited for web development. It then covers PHP fundamentals like syntax, variables, data types, operators, and control structures. The document also discusses how to connect to and query MySQL databases from PHP. It provides an example of building a simple user registration and login application with PHP and MySQL to store and retrieve user data from a database table.