On their contact page they give their address like this:
P.O. Box 12
123 Bingo St
Los Angeles, CA 90230
When writing the address on the envelope, which address to write? 123 Bingo St? or P.O. Box 12? or both? I've seen PO Boxes for mailing addresses before, but never together with a street address. Why would someone use both a PO Box and a street address? Is this common practice in the USA?
A street address is also to help promote the comfort of legitimacy. (So I have been told)
Looking for ESL work?: Try our EFL / TOEFL / ESL Jobs Section!
And what if someone give their address like, the corner of Bard and 5th Ave. (without the number of the building) Is that acceptable to write on an envelope for mailing?
If they don't provide building number, appartment number or suite number whichever is needed, your letter will not be delivered.
for example I have an address
It is not a suffix, it is an abbreviation for 'Court', one of the various terms we have for 'street'. Those people live in the house at 505 Decker Court.
Other street nomenclature: St (Street), Rd (Road), Ln (Lane), Circ (Circle), Ave (Avenue), Blvd (Boulevard), Wy (Way), Cres (Crescent), and others that do not come to mind at the moment.
Hope that helps!