The staining properties of pyro developers are different from developer to developer, but the main idea is how blue sensitive contact papers react to the color of the stain, which then acts as a contrast enhancer.
It can sometimes mask grain as well, although while contact printing, grain isn't going to be an issue.
I wish you the best of luck in your endeavor, but it looks as though you're in good hands, so I will rest assured that you will be well taken very good care of. Remember to experiment; but don't stray with your materials too much. Consistency really is the ticket to amazing prints, and a constructive and critical thought process about pushing the boundaries and limits of what's available to you. You learn more by screwing up sometimes than if you get it right all the time.
thanks Thomas, I'm trying to find a copy of G.H.'s "book of pyro"