PHP Data Objects (PDO) is a database access layer that provides a uniform method for interacting with various databases in PHP. It allows developers to write database-agnostic code, meaning the same code can work with different database systems, such as MySQL, PostgreSQL, or SQLite, without modification. PDO supports prepared statements, which enhance security by preventing SQL injection attacks. Using PDO, developers can easily connect to a database, execute queries, and fetch results in a consistent manner. It also offers features like error handling and transaction management, making it a robust choice for building database-driven applications in PHP.