Triodes are vacuum tubes that are widely used in electronics for amplification and switching purposes. There are several synonyms that can be used for the term "triodes," including vacuum tubes, electron tubes, thermionic valves, and triode valves. These synonyms describe the same electronic device, which consists of cathodes, anodes, and a grid that controls the flow of electrons. Triodes were invented in the early 20th century and were an essential component of early radio and television technology. Today, while solid-state electronics have largely replaced triodes, they are still used in specific applications, such as high-end audio amplifiers and guitar amplifiers.