In general, the word Sunnah means habit, practice, customary procedure, or action, norm and usage sanctioned by tradition. In specific, any time the word Sunnah is mentioned, it is to refer to Prophet Muhammad (s.a.w.). Here it means his sayings, practices, living habits. The Hadith are reports on the Sunnah.
The two major legal sources of jurisprudence in Islam are the Quran and the Sunnah.
The Sunnah may confirm what is mentioned in Qur'an, interpret and explain it, specify what is meant by some general verses, limit and restrict the meaning of some verse in it, or may explain something that has been revealed in Qur'an.
The Sunnah has a high authority in Islam; and Allah in many places in the Qur'an orders the Muslims to follow the teachings of Prophet Mohammad (s.a.w.).