What is the difference between postal service and private delivery service?

For Yale admission, it says that:
If you use the postal service for your mailing, you should send materials to the following address:

Office of Undergraduate Admissions
Yale University
P.O. Box 208234
New Haven CT
06520-8234

For material sent by private delivery service (United Parcel Service, Federal Express, DHL, etc.) you should use our street address:

Office of Undergraduate Admissions
Yale University
38 Hillhouse Avenue
New Haven CT
06511

Does USPS, Fedex, count as postal service?

'private' carriers such as the FX and UPS don't deliver to P.O. boxes, only street addresses....that's why the 2 seperate addresses

Private is normally for large expensive items of over 拢100 sent by private couriers that require a signature

Postal service is federal and they send mostly letters.

Although those couriers could also do it (Fedex, UPS), it would cost you more.

Postal service will always be federally sanctioned.

As well, although the USPS will also deliver parcels, it is not their main function, and they are not as consistent as the privitized delivery services.

postal is when the guy sprays the place down with automatic gunfire. private is when he just shows up in those cute brown shorts...

USPS (regular US mail) delivers to any address.
Privates (FedEx, UPS, etc) will not delivery to a PO Box - because they require a signature upon delivery.

Forget applying to Yale. Save your money for University of Phoenix.