Keno is a lottery-like gambling game often played at modern casinos, and also offered as a game by some state lotteries.
Players wager by choosing numbers ranging from 1 through (usually) 80. After all players make their wagers, 20 numbers (some variants draw fewer numbers) are drawn at random, either with a ball machine similar to ones used for lotteries and bingo, or with a random number generator.
Each casino sets its own series of payouts, called "paytables". The player is paid based on how many numbers were chosen (either player selection, or the terminal picking the numbers), the number of matches out of those chosen, and the wager.
There are a wide variety of keno paytables depending on the casino, usually with a larger "house edge" than other games offered by that casino. The house edge ranges from less than 4 percent to over 35 percent. The typical house edge for non-slot casino games is under 5 percent.