|(Contains One Each of an NPN & PNP Transistor)
(With Current Gain (hFE matched within 10%)
Complementary pairs, just means one is a PNP and the complement is NPN. They exhibit complementary specifications.
A Matched Complementary pair is the same idea but they are sold in sets of two or more. It means that the output from the NPN transistor has been selected to be close to the output of the PNP Transistor. Typically the outputs are matched to within 10% of each other.