PDO, or PHP Data Objects, is a database access layer in PHP that provides a uniform method for interacting with various databases. It allows developers to execute SQL queries and retrieve data in a consistent way, regardless of the underlying database system. This abstraction makes it easier to switch between different databases without needing to rewrite the entire codebase. One of the key features of PDO is its support for prepared statements, which enhance security by preventing SQL injection attacks. Prepared statements separate SQL code from data, ensuring that user input is treated as data only, not executable code. This makes applications more secure and reliable when handling database interactions.