The arithmetic
What is gambling?
Gambling is risking something of value on an uncertain outcome in the hope of winning more. Three parts: a stake, chance affecting the result, and a prize.
Take away any one of them and it stops being gambling. That is why a stock trade is not gambling and a raffle ticket is.
The three-part test
Stake: you put something up that you can lose. Chance: the outcome is not fully under your control. Prize: there is something to win.
Skill can be present and it does not change the classification. Poker and sports betting both reward skill enormously and both are still gambling, because chance decides individual results.
Forms it takes
Casino games against the house. Sports and event betting against a book or an exchange. Lotteries. Bingo. Poker against other players. And a growing category of arcade-style titles that are slots with a different animation.
Loot boxes and social casino apps sit in a grey area that regulators are still arguing about, and the distinguishing feature is usually whether the prize can be turned back into money.
What changed with phones
Every previous form of gambling required going somewhere or at least sitting down. An app is four centimetres from your hand and it buzzes during a game.
That is the difference this whole site is built around, and it is why the take a break page leads on deleting apps rather than on willpower. Friction is the useful variable and an app removes all of it.