What is the difference between a millah (religious community), a ta'ifah (sect/group), a firqah (division/faction), a nihlah (creed/doctrine), and a shari'ah (divine law)?

Al-Millah (creed/religion) and An-Nihlah (sect/creed) are terms used to refer to a religion. Ash-Shari'ah (divine law) linguistically means "the straight path," and technically it refers to what Allah has legislated for His servants in terms of religion and rulings. As for Al-Firqah (group/sect) and At-Ta'ifah (group/faction), they are parts of the Ummah (nation) distinguished by a particular methodology. The terms "the saved sect" (Al-Firqah An-Najiyah) and "the victorious group" (At-Ta'ifah Al-Mansurah) are applied to Ahlus-Sunnah wal-Jama'ah.