traceability matrix maps requirements with test cases.It is
used to find which testcase can be modified with respect to
requirement change.Golden bug can be determined only with
this matrix.golden bug is one which affects critical part of
the application.
   By preparing this we can ensure that we have covered all
functionalities specified by customer in our test cases.
for traceability matrix,
  1.create two dimensional table
  2.One row for requirement specification.
  3.one column for configuration item such as h/w device,s/w
modules.
  4.Put a check mark at the intersection of row & column if
configuration item satisfies the stated requirement.

Requirement tracebality Matrix basically gives the 
realtionship between requirements and test cases. At least 
one requirement should be mapped to atleast one test case. 
When all the test cases are run and passed that means all 
the requirements are met, hence good quality. At any time 
as we keep on tracking the requirmetns passed, we will come 
to know what are the cases that should be run to meet the 
other rquirments (whcih rre not met . This can be done in 
excel sheet as explained above.