The process is a bit complicated, but in brief form...
The plate has areas that accept water or not
the plate is wet
Then oil based ink is rolled over it sticking only to the dry areas. Regular image
Then the plate prints to a rubber roller -reversed
Then the rubber roller prints to the paper.- regular
The plate will be slightly bigger than the object being printed. Small stuff is usually done in sheets, with sheet size depending on how many you need to print and what size press you've got. The shop I worked for had 3 sizes, one did roughly 8 1/2x 11, another I think 16x24, and a few that did 23x35.
Topps has/had huge presses, capable of printing two 132 card sheets at once. About 44 x 58. All the aluminum cards we see are cut down from larger plates. In the case of 1962s there's no border because the cards had the woodgrain border. Modern stuff often has no border as well. Some of the new "printing plate" cards aren't actually from plates- the real plate won't say "printing plate" anywhere in the card image
The aluminum is thin but can be very useful. When Aluminum prices are down shops will sometimes allow the plates to be taken for other uses. I used the little ones as dustpans when sweeping up. And took a few for a friend of mine to use to cover rust holes on his car. RELAX! we didn't print cards. I think his car was fixed with an MIT course catalog or somethinglike that.
I'f we'd printed cards I'd have the plates
Steve B