A stall warning system is designed to alert the pilots of an impending stall, which occurs when the airflow over the wings becomes disrupted, causing a loss of lift. This can happen when an aircraft is flown at too low of a speed, or at too steep of an angle of attack. The stall warning system is typically triggered by a decrease in air pressure on the wing's leading edge, and it usually sounds an audible alarm and/or provides a visual warning in the cockpit.

It is important to note that the stall warning system is a warning system, and it does not prevent the aircraft from entering a stall, it's a reminder for the pilots to take action to prevent the stall from happening.