PHP is a widely-used, server-side, open-source programming language designed for web development. It can be used to create dynamic web pages, and it's often used in combination with the MySQL database and the Apache web server. It is particularly well-suited for creating dynamic, database-driven websites and has a large community of users and developers. PHP also has a wide range of libraries, frameworks and CMS like Wordpress, Magento, Laravel and many more. It is relatively easy to learn and use, and it's supported by most web hosting providers.