What is RTM (Requirement traceability matrix) and its importance?

In many companies testing starts only after the coding or execution phase of the project .If the companies are really want benefits from the testing of product, then testers must be involved initially from the requirement phase.

If the tester is involved from the starting from requirement phase, then requirement traceability matrix (RTM) is one of the most important reports that provides the detailed test coverage to the test cases.

In requirement traceability matrix (RTM), each test case is mapped to the each requirement. Therefore 100 % test coverage can be found out using the RTM and there is less chance for missing any requirement in testing. This is one of most important advantage of preparing the RTM.