What is airplane stall warning?

When an airplane is moving forward through the air at too slow a pace to continue flying A vacuum forms in front of the leading edge of the wing. A tube running from this point into the cabin the warning in a Cessna sounds like a party whistle. This is a particularly important tool while landing as it is important that air speed is maintained when you are close to the ground. When a plane stalls it dives downwards until it regains air speed, which I once found out, is really scary when you're about a hundred feet off the ground.