Controlled airspace is a designated area of airspace where air traffic control (ATC) services are provided to manage aircraft operations. This airspace is established to ensure the safe and orderly flow of air traffic, particularly in busy regions. Pilots must follow specific rules and obtain clearance from ATC before entering controlled airspace. There are different classes of controlled airspace, including Class A, Class B, Class C, and Class D, each with its own requirements for communication and visibility. These classifications help regulate the altitude and type of aircraft that can operate within them, enhancing safety for all users in the airspace.