Belief systems are a set of ideas, values, and principles that guide an individual or group's behavior. The term REL is a three-letter acronym for the word 'RELIGION, ' which is a type of belief system. RELIGION is a set of beliefs and practices that are based on a shared set of texts, traditions, and rituals. It is often used to explain the meaning of life, provide guidance on how to live, and offer comfort in times of distress.