AsianRunner answered correctly! And I just want to add that the purpose of a protein treatment is to bind to the hair, which makes it stronger, and in some cases, curlier.
Curly and PROUD!!!

My hair has a mix of low/med/high porosity, and it's medium textured (some are still fine, though!)

CG since Sept. 2011
Cowash: Vo5/Suave Naturals/Tresemme Naturals*
RO/LI: GVPCB*, Tresemme Naturals*
Low-poo: Shea Moisture Moisture Retention
Stylers: KCKT*, Coconut Oil, Olive Oil, Grapeseed Oil, Honey*

* represents my HGs!!! Finally!!!