The bipolar transistor, a key semiconductor device, is a three-terminal component crucial for amplification and switching applications. Fabricated from doped semiconductor materials, it operates utilizing both electrons and holes, hence 'bipolar.' Unlike unipolar transistors like field-effect transistors (FETs), which rely on a single charge carrier, bipolar power transistor employ the cooperation of electron and hole flows. 

They consist of the emitter, base, and collector regions, where a small base current controls a larger collector current, facilitating signal amplification or current switching. This versatility has made bipolar junction transistor indispensable in various electronic circuits and systems.