I hope I can properly phrase these questions so that they are clear. 
I want to know about "scratch off" lottery cards.  I notice on the
back they give the "odds of winning."  Are the cards generated by
randomly generating numbers (like a megamillions drawing) or are there
a certain number of "winner" cards generated and then randomly
distributed to the vendors (like the McDonald's Monopoly games)?  Why
does the former method seem "luckier" than the latter?  If the latter
method is used, how do I know that the winning cards are randomly
distributed?  Finally, when I cash in my (admittedly meager) winnings,
the clerk scans the card and the pay-out amount appears.  How do I
know that the clerk hasn't already scanned all of the cards, kept the
good ones for himself and sold me losers? (Sure seems like that is
what is happening!)

well- the clerk can not scan all the tickets ahead of time because
under the "part you scratch" are numbers the clerk needs to enter in
the computer after she/he scans the ticket to find out if it's a
winner or not.