Lock and key
Also said as Key and door, Ability gate
A gate that one specific thing opens. The key may be an actual key, or an ability that works as one: a hookshot, a double jump, a bomb.
It turns a map into a puzzle about order, and shows the player a door now that will pay off later. The designer's job is to make sure no key ends up behind its own lock.
Say it
“Show the player the red door in the first minute, then put its key at the far end of the east wing, so the second half of the level has a purpose.”
Where you’ve seen it
Doom hides red, blue and yellow keys around each level and colours their doors to match. Metroid-style games use abilities the same way, so every new power reopens the map you have already walked.
Not to be confused with soft lock
Lock and key is a design tool you use on purpose. A soft lock is the failure you get when the player can no longer reach a key they need.