Short answers, pulled from the story.
Gambling is the wagering of something of value on a random event with the intent of winning something else of value, where instances of strategy are discounted. It requires three elements: consideration, an amount wagered; risk, meaning chance; and a prize.
The legal gambling market totaled an estimated $335 billion in 2009. Gambling is a major international commercial activity.
The first known casino, the Ridotto, started operating in 1638 in Venice, Italy. Gambling itself dates back at least to the Paleolithic period, before written history.
Gambling dates back at least to the Paleolithic period. In Mesopotamia the earliest six-sided dice date to about 3000 BCE, and they were based on astragali dating back thousands of years earlier.
Religious views vary widely. The Buddha named gambling a source of destruction in the Singalovada Sutra, ancient Jewish authorities disqualified professional gamblers from testifying in court, and there is consensus among the Ulema that gambling, called Maisir in Arabic, is haraam. The Catholic Church holds there is no moral impediment so long as the gambling is fair and the gambler can afford to lose.
In many American states one must be over 21 to enter a casino, but may buy a lottery ticket after turning 18. The gambling age can differ depending on the type of gambling.
Gamblers tend to prefer likely outcomes and favorites, exhibit optimism by overestimating desired events, and resist betting against teams tied to their identity. More than 45% of NCAA fans in two studies turned down a free real $5 bet against their team, and the ratio bias leads people to prefer worse odds drawn from a larger sample.