As Hellion already mentioned, it's about medical treatment.
I believe it's used primarily in the U.S. where you're not covered by a national (or otherwise common) health insurance. If you lack medical insurance, the hospital is only required (by law) to treat the critical condition, and may then release you.
An (unqualified) address can be a post-office box or APO address or the like — any place that can receive mail. People often use "street address" when they need to be able to find a person there, e.g. for packages that require signatures.
Actually both expression mean the same: a continuous movement on the road. In "along" is contained "long", so one may guess the idea is "(on) the length of the road" or in "along the river" "(on) the length beside the river". A verb of movement + down normally describes a mouvent from a higher point to a lower point. But it is also used for horizontal movement.
Best Answer
As Hellion already mentioned, it's about medical treatment.
I believe it's used primarily in the U.S. where you're not covered by a national (or otherwise common) health insurance. If you lack medical insurance, the hospital is only required (by law) to treat the critical condition, and may then release you.