What is meant by the regression testing?

The regression means testing again the unchanged component of the application where the test cases are re-checked in the order to inspection whether the previous functionalities of the application is running fine or not and to ensure that the new changes are not make any new bugs. This regression testing can be performed on a new build when there is a slight change present in the original functionality or when there is a single bug to fix. The regression testing tools is called as the verification testing in which it ensures that the newly made changes are not affecting the original application. The testers perform the functional or regression testing when a new build is available for verification process and the intent of this testing is to verify the changes made in the existing or previous functionality and the new functionality. 

When this testing is done the tester should verify that whether the existing functionality is working as expected and new changes introduced should not defect the functionality of the working. The regression testing is a part of testing that is done at the time of the release cycle and it is also considered in the test estimation process where the regression testing is usually done after verification of changes or after adding new functionality to the system or application. But this is not followed for the all cases because the releasing of the product takes months to complete so this testing is done at the daily process to ensure the effects of the changes made to the system so that the developer can update the functionality before releasing the application or product.