Wow our culture today! My stars.
It's my interpretation that the protagonist in question provides oral sex to the lady and stimulated her clitoris in ways her jock boyfriend never thought or knew how to. It's my understanding she definitely enjoyed that. It is also my understanding that she was not too pleased to find out who was behind the mask at first.
It's further my understanding that Revenge of the Nerds II: Nerds in Paradise (1987) [1] intimates that they then became something of an "item" (in today's terms that means they dated!).
Finally, it's my understanding that it's a fun movie and not a manual for life.