-DUT monitor component. A component that keeps track of all defined monitor points during the course of verification testing. This component tell exactly how much functional coverage has taken place over the course of the simulation test suite.
-DUT checker component. A component that verifies the actual functionality exhibited. A checker component could range from a simple 1-method checker to a multiple-file hierarchical checker that verifies multiple facets and functionalities of the DUT. Checkers can verify at least two different aspects of DUT operations. Did the correct operation happen? Did it happen in the correct time window?