A klystron is a type of vacuum tube used to amplify radio frequency signals. It works by using a stream of electrons to produce microwave energy, which is essential in various applications like radar and satellite communications. Klystrons are known for their ability to generate high power and are often used in broadcasting and particle accelerators. These devices operate by modulating the electron beam, creating oscillations that can be harnessed as amplified signals. Klystrons are crucial in technologies involving microwaves, such as television transmitters and communication satellites, making them important in modern telecommunications.