A pitot tube is a device used to measure fluid flow velocity. It consists of a tube with an open end facing the flow and a side opening that measures static pressure. By comparing the pressure at these two points, the velocity of the fluid can be calculated using Bernoulli's principle. Commonly used in aviation, the pitot tube helps determine the airspeed of an aircraft. It is often found on the exterior of airplanes, where it can accurately gauge the speed of air flowing over the wings, contributing to safe flight operations and navigation.