UPS is a publicly-traded company (ticker: UPS) that stands for United Parcel Service. USPS stands for the United States Postal Service and is a quasi-governmental agency. USPS is self-funded through the sale of postage stamps and delivery services. There is little difference between the two shipping services. However, USPS Priority mail is generally guaranteed to reach its destination within 2-3 business days, and UPS Ground can sometimes take up to 2 weeks.