A Venturi device is a simple tool used to measure fluid flow or to create a pressure difference. It consists of a tube that narrows in the middle, causing the fluid to speed up as it passes through. This increase in speed leads to a decrease in pressure, which can be measured to determine the flow rate. The Venturi effect is the principle behind this device, illustrating how fluid dynamics work. It is commonly used in various applications, including carburetors in engines and water flow meters in plumbing systems, making it an essential component in engineering and fluid mechanics.