Just pointing out that there is a difference - to those that don't know how the two motors work.
A petrol engine is fed more air and it meters the fuel to make the correct mixture whereas -
A diesel is fed more fuel and it meters the air to make the correct mixture.
It's not that it was a stupid question (There are none except if you are trying to troll). The reason I gave really simplified answer was that if I would have answered using physical phenomenons, differential mathematics, integration and all that how I can prove how throttle works, it would be so complex answer that no-one benefits from it.
After all, we don't know why he asked that question. Maybe because he doesn't know what word "throttle" means...