Reading "What are the rules of keno?" starts with the family it belongs to. Every casino floor carries a few games that are neither cards dealt to a hand nor a wheel with a ball in it. Keno, bingo and scratch cards all work by matching numbers or symbols already decided somewhere else, and casino war sits beside them as the shortest game in the building. They share a shape: the player commits first, and the result arrives in one step.
Bingo replaces the pick with a printed card and the draw with a caller. Numbers come out one at a time and each player marks a card against them until a pattern completes — a line, two lines, or the full card. A ninety ball game and a seventy five ball game differ in the size of the field and in the patterns that count, which is why the rules sheet matters more than it looks.
Casino war is the card game of childhood with a stake on it. Both sides get one card, the higher wins, and a tie offers either surrender for half or a raise to fight it out. A tie is far commoner here than at a card table, since only the rank matters and suits are ignored. Those tie rules carry the whole game: the raise is the only decision in it, and the house keeps its margin almost entirely from what happens when the two cards match.
What these four have in common is where the thinking happens. There is no strategy inside a keno draw or a bingo call, and none inside a scratch card, so whatever a player can control is decided before the round — how many spots to take, which card to buy, whether to go to war. The pay table and the rules sheet are where the differences live, rather than in the play.
When both cards match in rank, the player chooses to surrender half the stake or raise and go to war; the house draws most of its margin from ties.
Every choice comes before the round: how many keno spots to take, which card to buy, or whether to go to war, since the draw itself allows no strategy.
The player picks a handful of numbers from a field of eighty, twenty are drawn, and the payout depends on matches and on how many were picked.
The two games use fields of different sizes and count different patterns as wins, which is why the rules sheet for each matters more than it seems.
Matching four of five picks is a different prize from matching four of eight, so each spot count gets its own column, and venues can pay quite differently.