PHP is a programming language that is primarily used for web development. It can be used to create dynamic web pages and can interact with a variety of databases, including MySQL, Oracle, and PostgreSQL. With PHP, you can create forms, manage user sessions, validate form data, create cookies, and perform a wide range of other tasks. PHP is also used for creating and manipulating images, generating PDF files, and sending emails. It is a flexible language that can be used for a wide range of applications.