Regression testing is meant for regression defects. Regression defects are defects due to which the functionality which was working first normally has stopped working. This is probably because of changes made in the program or the environment. To uncover such kind of defect regression testing is conducted.
Below figure shows the clear explanation and difference between regression and confirmation testing. If we fix a defect in an existing application we use confirmation testing to test if the defect is removed. It’s very much possible because of this defect or changes to the application it can affect other sections of the application. So to ensure that no other section is affected we can use regression testing to confirm the same.
Regression testing in action