"You don't have to sit down there babe."

He waves her over to sit with him.

"I will show you what a rotary engine is."

He pops up an image of a rotary 2 rotary engine.

"That is a 2 rotor.  A rotary instead of having pistons has a set of rotors which turn inside the engine."

He shows a picture of the rotors inside the engine.

"Quite different huh?"