Can someone explain American door numbers

Whenever i watch anything showing a house front in America its door number is at least 4 digits.

If they have that many houses in one road you would never know who lives in your street, postman would only deliver to about 2 roads. You wouldn't say to the kids, just stay in the street.

Am i missing something???

Generally the first two or three numbers are the number of blocks the cross street is from a designator road. For instance, 1711 is the block after 17th Avenue. The second set of number is the number of the house on the block. Odd number on one side of the street, even the other. The roads/Streets/Avenues etc can run from state to state so quite possibly there can be that many houses along the road but just sectioned into blocks.
Then you get Avenues, Streets, Row etc. There are two groups of these one group runs N to S and the other E to W.

eg. my Dads address is
8013 NW (80th block)
103rd Avenue (Street name)

Thanks, the blocks make sense, interesting stuff. Wouldn't have thought many would have known that.