What is Requirement Traceability? Explain its importance.

Requirement Traceability is mapping of needs to test cases. There are two major traceability: Forward and Backward. It is significant to know whether all the requirements mentioned in the Requirement Document have a corresponding test case or not. At the similar time, it is significant to know which requirement a particular test case has been written for. These are vital if there are any changes in the requirement, we should know which test cases require to be re-written or modified