Complex sentence: "austere", "fundamentalist", "puritanical" (or "puritan"), describes an Islamic "reform movement" to restore "pure monotheistic worship", or an "extremist pseudo-Sunni movement".
Split into simpler sentences: austere, "fundamentalist", "puritanical"(or "puritan"). It describes an Islamic "reform movement"to restore "pure monotheistic worship", or an "extremist pseudo-Sunni movement".