Final answer:
Regression testing is a software testing technique used to verify that changes made to a system have not caused any errors or 'broken' previously working code.
Step-by-step explanation:
Regression testing is a software testing technique used to verify that changes made to a system have not caused any errors or 'broken' previously working code. It involves re-running tests that were previously passing to ensure that they still pass after the changes have been made. This helps ensure that the system continues to function correctly and that the changes have not introduced any unintended side effects.