Voltage
The electrical potential difference between two points.
A symbolic voltmeter connected across two terminals measures their potential difference.
Voltage measures electrical potential difference, in volts. Grid equipment operates at specified voltage levels, which are changed by transformers as power moves through the network.
A difference between two points
Voltage is always measured between points, such as two phase conductors or a phase and neutral. A voltmeter connects across those points; a voltage is not a quantity that flows along a wire.
Grid voltages are commonly stated in volts or kilovolts. For AC, the quoted value is usually an RMS value: the equivalent DC value for producing the same average heating in a resistor. A rating must also specify whether it refers to phase-to-phase or phase-to-neutral voltage.
Why it matters
Voltage ratings help determine insulation, equipment compatibility, and how different parts of a network can connect.