It's there to do exactly as the name implies. When you depress the pedal when cold, the choke flips closed. In Theory, you're supposed to now start the engine without hitting the pedal and it will start and idle. Being a carburetor, it usually doesn't work that easily although some do. Once it's running, you blip the throttle and the choke pull off will pull the choke in the open position, so that you can drive it. It's another part of our "hurry up" world so you don't have to sit there and wait for warmup. lol