what is usps priority mail is a service offered by the United States Postal Service (USPS) that provides fast and reliable delivery for packages and letters. Priority Mail offers delivery within 1-3 business days, depending on the destination, and includes free tracking and $100 of insurance coverage for eligible items. This service is often used for time-sensitive deliveries that need to arrive quickly. USPS Priority Mail is popular for both domestic and international shipments due to its efficiency and cost-effectiveness for medium-sized packages.