Postpaid is a billing plan commonly used by mobile phone service providers, where customers pay for their usage at the end of a billing cycle. This means users can enjoy services like calls, texts, and data without worrying about running out of credit, as they receive a monthly bill detailing their usage and charges. In a postpaid plan, customers typically sign a contract for a specific duration, often receiving benefits such as discounted devices or additional features. This contrasts with prepaid plans, where users pay in advance for services and must manage their usage to avoid running out of credit before the next payment.