A delivery point is the smallest unit a postal service delivers to: one letterbox, one door, one box at a counter. An address names a delivery point; a building may contain hundreds of them.
What Spaw answers
address_type names the kind of delivery point an address describes, in one of nine values: street, po_box, private_mailbox, general_delivery, rural_route, military, parcel_locker, bulk_mail or unknown. address_type_source says what settled it — address_rules when the operator's own naming conventions did.
Four of the nine carry weight on the risk score: a private mailbox +60, general delivery +40, a PO box +30 (zero in the nine countries where a box is the ordinary way to receive mail) and bulk mail +20. None of them is a fault. They are all real delivery points that a postal service serves; the weights exist because a parcel courier, a KYC check and a marketing list want different things from an address.
What the field is not
It is not a deliverability answer. Whether post actually arrives at a delivery point is a licensed check that this service does not run: deliverability_checked answers false and is_deliverable stays null rather than guessing.
And nothing in an address answer says who is behind the letterbox. The product is about places.