Difference between Retesting and Regression Testing

Definition of Retesting and Regression Testing:

Re-Testing: After a defect is detected and fixed, the software should be retested to confirm that the original defect has been successfully removed. This is called Confirmation Testing or Re-Testing

Regression testing:  Testing your software application when it undergoes a code change to ensure that the new code has not affected other parts of the software.

It can be done in 2 scenarios:

1) When ever test engineer identified a defect, after rectification once
again we need to test the defected functionality as well as its related
functionality.

2) When ever some new features are added to the application then we need to
test the related functionalities of those new functionalities.

The defect logged by tester while testing application and same fixed by developer. In Retesting we check same defect whether fixed or not using steps to reproduce mentioned in the defect. In Regression testing we check same defect fixes are not impacted other unchanged part of the application, not breaking the functionality working previously and break due to fixing defect.