Sunna means the trodden path — the Prophet's practice, recorded in hadith, covering how he prayed, ate, judged, married, forgave, and slept. Sunni Islam takes it as the second source of law after the Quran and as the model for ordinary conduct, which is why questions Westerners would consider matters of taste (beard length, which hand to use) can carry religious weight. The name of the branch is the practice: ahl al-sunna, the people of the path.