Voltage is the electrical "push" in a wire or a battery, measured in units called volts. Think of electricity as water in a pipe: voltage is how hard the water is being pushed. Low voltage (a small battery, 1.5V) pushes gently. High voltage (a power line, thousands of volts) pushes hard enough to kill you. That is why you see it on warning signs: HIGH VOLTAGE. In everyday life you meet the word mostly on machines and travel plugs: Taiwan uses 110 volts, most of Europe uses 220, so people say "check the voltage before you plug it in" or "this hair dryer is dual voltage." It is normally uncountable — "the voltage is too high" — but engineers do say "different voltages" when they mean several different levels. There is also a loose, non-electrical use, though it is not common: people sometimes say a room or a performance has "high voltage" to mean it feels exciting and full of energy. That use is a bit dated now, and you will meet it more in writing than in speech.