Functional testing is a type of software testing that verifies if a system or application behaves as expected according to its specified requirements. It focuses on testing the functionalities of the software by providing appropriate input and checking the output against the expected results. This ensures that each feature works correctly and meets user needs. The process typically involves creating test cases based on the software requirements and executing them to identify any defects or issues. Functional testing can be performed manually or through automated testing tools, and it is essential for ensuring the quality and reliability of the software before it is released to users.