When a bipolar transistor is used as a switch, which electrode controls its state?

When a bipolar junction transistor (BJT) functions as a switch, it toggles between two distinct states: saturation (fully on) and cut-off (fully off). This state is determined entirely by the amount of current applied to the base terminal. By injecting a sufficient current into the base, the transistor acts like a closed switch, allowing current to easily flow from the collector to the emitter. Removing the base current completely stops this flow, turning the switch off. The "Gate" is a common distractor as it is the control terminal for a field-effect transistor (FET), but BJTs use a base.