Weighing up "How bingo cards work?" takes one look at the draw. Keno, bingo and scratch cards are the number games that sit closest to a lottery. Each one draws or reveals numbers at random, pays by a fixed table and asks nothing of the player beyond a choice of numbers or a ticket. What they pay, whether they can be rigged and how they work online explains why they are popular and why they cost more than they seem.
Lottery scratch cards work from a print run whose number of winning tickets is fixed before any card is sold. Each card is printed as a winner or a loser; scratching only reveals which. They are not rigged in the sense of changing results, but the odds are set in advance and printed on the back or on the lottery's site, and many prizes simply return the price of the ticket. Buying late in a run changes nothing a buyer can see.
Bingo is gambling wherever cards are bought for money and prizes are paid in money, even when it is played as a social game. A bingo game does pay, but prizes come from the pool of card sales minus the operator's share, so the more players join a session the larger the prizes and the longer the odds. Online bingo games cannot be rigged where the draw is certified, although unlicensed rooms offer no check of that kind.
No keno numbers hit the most over time; each draw is independent, and any number that has come up often recently is just as likely as any other in the next draw. Players asking what numbers they should pick are really choosing how many: picking more spots changes the pay table and the odds, while which spots are chosen makes no difference. Birthdays and lucky numbers are as good as any, and just as bad.
Yes, the number of winning tickets in a print run is fixed before any card is sold, and scratching only reveals whether a card was printed a winner.
Keno keeps among the highest edges in any casino, often twenty percent or more, which makes it better suited to small stakes and patience.
Bingo prizes are paid from card sales minus the operator's share, so more players in a session mean bigger prizes and longer odds for each card.
Licensed draws come from a certified generator or a filmed ball machine, so the operator cannot rig them; unlicensed rooms offer no such check.
Which numbers are chosen makes no difference; how many spots are picked changes the pay table and the odds, and birthdays are as good as any.
No keno number hits more over time, because every draw is independent and a number that appeared often lately has the same chance next draw.