RTM is a technique used for gathering the requirements, which is called as requirement
traceability matrix. Once all the requirements are gathered using the
traceability method mentioned, user can write test cases based on the gathered requirement and mapped these with the requirement which helps the user to know whether all the requirements are covered or not.

Once user is assured that all the requirements are gathered. He/She can execute those test cases and on failing of any test cases he/she can map it with the associated test case, which is further mapped with the requirement.

In the mentioned way user can relate the test cases, requirements and defects with each other.