Garage door extension springs use resistance to help a door function. They’re tightly coiled and extend and retract as a garage door operates. In general, extension springs return a moving object to its original position. Something moves, which extends the spring, and the resistance in the spring pulls the object back. That’s how garage springs work. 

Garage door Standard extension springs are coiled accessories installed above the door's horizontal track. When the door is opened, the energy stored in the extended springs is used to lift the door.