A transistor

is a semiconductor device used to amplify or switch electronic signals and electrical power. It consists of three layers of a semiconductor material, usually silicon, with two layers forming a junction called the base-collector junction, and another junction called the base-emitter junction. Transistors can be used in various electronic devices such as amplifiers, oscillators, and digital switches. They are essential components in modern electronic circuits and play a crucial role in the functioning of electronic devices.