A transistor radio is a small, portable device that uses transistors to amplify radio signals. It allows users to listen to AM and FM radio broadcasts without needing a large, bulky setup. The invention of the transistor in the 1940s made it possible to create compact and energy-efficient radios, revolutionizing how people accessed music and news. These radios typically run on batteries, making them convenient for outdoor use or travel. The introduction of the transistor radio in the 1950s led to a surge in popularity, as it provided a new way for people to enjoy entertainment on the go, influencing the development of personal audio devices like walkmans and smartphones.