High concept
Also said as Hook, Elevator pitch, One-line premise
A premise so clear it can be understood and wanted from one sentence. It gives everyone on the team the same picture of the game.
If you cannot say it in a sentence, you will struggle to sell it, and your team will each build a different game. It also works as a filter, since any feature that does not serve the line is suspect.
Say it
“Pin the high concept to one sentence: "You run a ferry across the river of the dead, and you cannot refuse anyone." If a feature does not serve that line, it goes.”
Where you’ve seen it
Superhot: time moves only when you move. Papers, Please: you are a border inspector in a failing state, checking passports. In each case the one line tells you the verbs, the tension and why you would want to play.
Not to be confused with tagline
A tagline is a piece of marketing that can be written after the game is finished. A high concept is the idea the game is made from.