Foldback
Also said as Branch and bottleneck, Bottleneck, Gated branching
Branches rejoin at a shared scene, so the writing stays affordable. Flags carry what you did through the join. Chris Crawford named it, and he thought it cheated.
It is how nearly every story-heavy game pays its bills. Without flags, though, a foldback quietly erases the choice before it, which was Crawford's complaint.
Say it
“Fold both paths back at the gate scene. Keep a "paid" flag and a "showed letter" flag, and write one extra line in the gate scene for each, so it still feels like your journey.”
Where you’ve seen it
In The Walking Dead by Telltale, you save either Carley or Doug in the first episode. Whichever you saved is shot in the third, and the story carries on along one line.
Not to be confused with illusion of choice
With a foldback, the paths really do differ before they rejoin, and flags can carry that forward. An illusion of choice never differed at all.