Procedural generation
Also said as Procgen, PCG, Roguelike levels
Content made by an algorithm rather than by hand, at build time or as you play. The craft is in the rules around the randomness, since pure randomness rarely gives you a good level.
It buys replayability and scale that no team could build by hand. The danger is that everything looks different and feels the same, and that it can make things that are impossible to finish.
Say it
“Generate the route first, then fill the rooms, so every level can be finished without bombs. Add a check that walks it, and throw away any level that fails.”
Where you’ve seen it
Spelunky builds each level from a 4 by 4 grid of rooms: it walks a route from top to bottom first, then fills in rooms from templates that keep that route open.
Not to be confused with random
Random is a dice roll. Procedural generation is a set of rules that uses dice rolls and guarantees what must hold: there is an exit, and you can reach it.