The Civil Aviation Authority (CAA), is the publicly owned organisation in charge of flying (Aviation) in the United Kingdom. It was created in 1972, doing the tasks previously done by the Department of Transport.
This means it is in charge of:
The CAA no longer provides air traffic control services (ATC), this responsibility was passed to a private company called National Air Traffic Services (NATS) in 2001 which the government owns 49% of.
Some other duties have passed to the European Aviation Safety Agency (EASA), such as type certification. CAA-UK is part of the rulemaking group of the EASA.