*the postal service does not pick up mail from your home (unless you pay for and order courier service).
*they deliver every day except saturday. (I think).
*most people live in apartment buildings so they are put in the individual mail boxes in the lobby. in some smaller towns/rural areas they deliver to a central distribution point in the neighborhood (you still get your own mail box that is locked but you have to go and get the mail).
*in really rural places, they have somthing called "mobile mail" which is a little truck (think of an ice cream truck) that drives around to small places and deliver mail and packages, sell stamps, do the postal bank stuff etc. when we lived in such a place, they used to come every day except saturday but that was 18 years ago, not sure what the story is now.
*most cities have at least one post office, many cities have post offices in each neighborhood. you can buy stamps, send packages, use the postal bank, wire money, buy cards for cell phone, fill up your parking gadget etc. lately they are also offering business services such as printing envelopes and stationary etc.