Can anyone explain the difference between potatoes and seed potatoes?

I just bought organic seed potatoes from Wood Prairie Farm in Maine - a place I've bought from before, with a wide range, if now dwindling (at this late date), choice of potatoes.

Now, I know I could Google to get the answer but wonder if my astute readers (farmers among them) could provide the answer in the comments.

I think I am going to grow these in an expandable bin. This article explains how you can get 100 pounds in a 4x4x4 bin. I don't need that many so am trying a 2x4 footprint if I can get my act together and build it.

- Samuel Fromartz