I've attached a scan of a handout I recently received which neatly maps the process at a high level of how the PDP process works in the GNSO.
I hope this is handy. We are working on producing more of this kind of information, with accompanying descriptions, to make processes like this easier to understand.
-- Regards,
Nick Ashton-Hart Director, At-Large
ICANN
PO Box 32160 London N4 2XY United Kingdom Main Tel: +44 (20) 8800-1011]