Backtracking
Also said as Retreading, Going back the way you came
Sending the player back through a place they have already been. Done well, the place has changed or they have: new powers open new doors. Done badly, it is the same corridor again with nothing to do.
It gets more use out of everything you built, and returning to a place you once found hard shows you how far you have come. The cost is walking, so it needs either something new on the way or a quick way through.
Say it
“The way back from the boss is 90 seconds of empty corridor. Add a lift back to the hub, or change the corridor: flood it, and put new enemies in it, so it is not the same walk.”
Where you’ve seen it
Metroid Prime ends by sending you back across the world to hunt twelve Chozo Artifacts, which many players found the weakest part of a game that otherwise uses returning so well.
Not to be confused with exploring
Exploring takes you somewhere new by your own choice. Backtracking takes you somewhere old, usually because the game requires it.