priority first class mail is a popular USPS service that provides fast delivery of letters, packages, and small parcels within the United States. The USPS offers both First Class Mail and Priority Mail services, with First Class Mail being the more affordable option for smaller and lighter items. Priority Mail, on the other hand, offers faster delivery times, typically 1-3 business days, with added benefits like tracking and insurance. The decision between First Class Mail and Priority Mail often depends on the size and weight of the shipment, as well as the urgency of the delivery.