Muslims: Is Hadith considered authoritative?

hadith means the things which prophet mohammed said and sunnah means the things which mohammed did a lot of hard work has been done to collect the hadiths and sunnahs and its all done by very religious ppl who loved the prophet ppl went on long journeys when they found out that a man has a hadith or sunnah in the begaining the hadiths and sunnahs were writen on leaves or the wooden pealing of trees then when the paper was invented it started coming in the books