Update: I had a UPS package returned to sender (side note: they suck and given a choice I will not use UPS ever). I would recommend putting PMB (private mailbox number) in Address1 instead of Address2.
What really is the difference between Address1 and Address2 and is it significant?
It depends on the country but generally (e.g. US)
* Address1 is expected to have Street Number, Street Name, or maybe PO Box or PMB (Private Mail Box)
* Address2 refers to Apartment, Floor, Suite, Bldg #
NO, Address2 is not asking for a secondary address or a backup of whatever you put in Address1. Neither is it a “confirm” address field. Nor it is simply a “continuation” of Address1
And also, if there is no company field Address2 will be a better place to write the information on than the Address field. Seems to differ by carrier, I suggest putting in Address1 for UPS.
Safe to say that Address1 should be general (but enough to pinpoint a geographical location – and obviously not include City, State, ZIP, Country) while other extra information should be in Address2.
Address2 fields in forms are generally (and for usability) shorter and in my opinion should have at least include hints as to what goes to it.
Also, for US ZIP code lookup you might find the following link from USPS helpful : USPS ZIP Code Lookup