What is a Difference between Regression and Retesting?

Regression testing is the testing of an application that verifies that there is no adverse effect of the changes made due to defect fix or change request to other areas of application. regression testing involves test cases other than those that are related to defect or change as per client request, but it also tests features that directly or indirectly connected with the feature that was rectified by developer against the defect raised, such as integration tests, test case related to web components and their functions along with those involved directly with defect raised. Regression testing is usually car ried out using automated scripts by selecting test cases and re executing the scripts to run those test cases.
Retesting is a testing to make sure that previously failed test cases due to defect are passed and the defect has been resolved. The test cases involved in retesting focus only on the failed test cases due to the defect or the scenarios or steps followed result in failed functionality. It is better to carry out manual testing in case of retesting to make sure that defect has actually been resolved.