How can you straighten hair permenantly, what is this chemicaly straightenign hair?

I have a freind who has really curly, fuzzy, afro type hair, he has tried everything, relaxing creams, hair straghtenig machines (which he has to use eveyrday to make it straight) but they still dont give the desired effect, i mena during the day the hair will rise up slowly , like fuzzy, and whats this chemical strightenign hair? what do they do there, if u shnmpoo ur hair doesnt it get back to being natural?.