difference between rebounding and relexing hair?

i have really frizzy curly hair. i want to get them straight. i was watching a morning show few days ago where they were talking about hair relaxing being better than hair rebounding. i was wondering what is the difference between two? i presume that rebounding is pin straight hair where relaxing will just take the frizz out and make hair more manageable. is that correct?
please help me understand this.
thanks