Gambling is the wagering of money or something of value (referred to as "the stakes") on an event with an uncertain outcome with the primary intent of winning money or material goods. Gambling thus requires three elements be present: consideration, chance and prize.[1] The outcome of the wager is often immediate, such as a single roll of dice, a spin of a roulette wheel, or a horse crossing the finish line, but longer time frames are also common, allowing wagers on the outcome of a future sports contest or even an entire sports season.

The term gaming[2] in this context typically refers to instances in which the activity has been specifically permitted by law. The two words are not mutually exclusive; i.e., a "gaming" company offers (legal) "gambling" activities to the public[3] and may be regulated by one of many gaming control boards, for example, the Nevada Gaming Control Board. However, this distinction is not universally observed in the English-speaking world. For instance, in the United Kingdom, the regulator of gambling activities is called the Gambling Commission (not the Gaming Commission).[4] The word gaming is used more frequently since the rise of computer and video games to describe activities that do not necessarily involve wagering, especially online gaming, with the new usage still not having displaced the old usage as the primary definition in common dictionaries.

Gambling is also a major international commercial activity, with the legal gambling market totaling an estimated $335 billion in 2009.[5] In other forms, gambling can be conducted with materials which have a value, but are not real money. For example, players of marbles games might wager marbles, and likewise games of Pogs or Magic: The Gathering can be played with the collectible game pieces (respectively, small discs and trading cards) as stakes, resulting in a meta-game regarding the value of a player's collection of pieces.

Many jurisdictions, local as well as national, either ban gambling or heavily control it by licensing the vendors. Such regulation generally leads to gambling tourism and illegal gambling in the areas where it is not allowed. The involvement of governments, through regulation and taxation, has led to a close connection between many governments and gaming organizations, where legal gambling provides significant government revenue, such as in Monaco or Macau, China.

There is generally legislation requiring that the odds in gaming devices are statistically random, to prevent manufacturers from making some high-payoff results impossible. Since these high-payoffs have very low probability, a house bias can quite easily be missed unless the odds are checked carefully.[8]

Most jurisdictions that allow gambling require participants to be above a certain age. In some jurisdictions, the gambling age differs depending on the type of gambling. For example, in many American states one must be over 21 to enter a casino, but may buy a lottery ticket after turning 18.

Because contracts of insurance have many features in common with wagers, insurance contracts are often distinguished under law as agreements in which either party has an interest in the "bet-upon" outcome beyond the specific financial terms. e.g.: a "bet" with an insurer on whether one's house will burn down is not gambling, but rather insurance — as the homeowner has an obvious interest in the continued existence of his/her home independent of the purely financial aspects of the "bet" (i.e., the insurance policy). Nonetheless, both insurance and gambling contracts are typically considered aleatory contracts under most legal systems, though they are subject to different types of regulation.