USPS stands for United States Postal Service. This service provides mail to people all over the United States.
Mail is carried and transported by train, ship, airplane, truck, and delivery vehicle.
Mail is ordered, transported by either a ship or an airplane. The mail is then transported by either truck, or airplane. Next, the mail is transported by several trucks, and finally delivered to the recipient by a delivery vehicle.
The USPS was created by the United States Congress. The USPS has security that checks mail, and if there is something illegal, it will be given to Forensic Scientists to analyze, test, and determine what the item is and how it connects to a certain case.