It's a test design technique, a two-test combination method for detection of defects. It is based on the observation that the most defects are caused by the interaction of no more than two factors (defects that occur when three or more factors interact are usually less critical). Test scripts are designed in such a way as to execute all possible individual combinations of each pair of input parameters. Therefore, a pair of two test parameters is selected and all possible pairs of these two parameters are sent as inputs for testing. Pairwise testing reduces the total number of test cases, thereby reducing the time and cost spent on testing.
