What is Traceability matrix? How can we use it?

Please explain What is Traceability matrix? How can we use it in our requirements? What is the benefit of this tecnique.

A traceability matrix is a table that is helpful in tracing a requirement to the tests that are needed to verify that the requirement is fulfilled. A good traceability matrix will provide backward and forward traceability, i.e. a requirement can be traced to a test and a test to a requirements. The matrix links higher level requirements, design specifications, test requirements, and code files. It acts as a map, providing the links necessary for determining where information is located.

The use of traceability matrix is that it helps to make sure that the approved requirements are addressed/covered in all phases of development: From SRS to Development to Testing to Delivery.