Countdown dynamic is where someone has a time limit to complete a quest or a race.This mechanic is commonly used for many racing games,action games and adventure games.The mechanic can be used in many different situations one of those are puzzles. some puzzles can be time restricted and you have to complete that puzzles in a certain amount of time you will mostly see this mechanic in the tomb Rader games or the uncharted franchise.
Example about this mechanic.
I walk into a cave and I see a pile of gold on a statue I began to run to the pile of gold to take it for all myself. As I removed the gold from the statue A trap was triggard and I only had a few minutes to solve the puzzle in front of me so I can survive the tarp.