Vertical speed refers to the rate at which an aircraft ascends or descends, typically measured in feet per minute (fpm) or meters per second (m/s). It is an important parameter for pilots, as it helps them maintain safe and efficient flight profiles during takeoff, landing, and cruising. In aviation, vertical speed is monitored using an instrument called a vertical speed indicator (VSI). This instrument provides real-time feedback on whether the aircraft is climbing, descending, or maintaining level flight, allowing pilots to make necessary adjustments to their altitude and flight path.