Grob Tutor question

[Riskman]

I've mentioned elsewhere that I'm an instructor with the Air Cadets hence the question.

Part of the syllabus covers the Grob Tutor and the engine controls are described as Throttle, Mixture and RPM.

Throttle and mixture I'm happy with but the book doesn't describe what exactly the RPM control does. I thought the throttles did that ie push forward = increased rpm so I assume it's something to do with the prop.

Does the RPM control enable the pilot to adjust the prop rpm through a gearing mechanism? Is this the modern equivalent to coarse/fine pitch?

Thanks in advance