Gating
Also said as Progression gate, Hard gate, Soft gate
Anything that stops the player going further until they have done something. A hard gate cannot be passed at all. A soft gate can be, but it is dangerous or expensive to try early.
Gates decide the order in which the game gets experienced, so abilities and story arrive in a sequence you can design for. Too many, or too obvious, and an open world feels like a corridor with scenery.
Say it
“Put a hard gate at the end of the first region, a cliff you need the grappling hook for, so everyone gets the same first hour. After that, use soft gates only: strong enemies that a good player can sneak past.”
Where you’ve seen it
In Metroid a low tunnel near the start of the game stops you until you collect the Morph Ball. Breath of the Wild keeps you on the Great Plateau until you earn the paraglider, then gates almost nothing else.
Not to be confused with lock and key
Gating is the general idea of holding the player back. Lock and key is one way of doing it. A boss, a skill check or a strong enemy can be a gate with no key anywhere.