VAC would be the abbreviation of Volt Altern Current which would be translated Volts of alternating current. The difference between VDC is that its sinusoidal oscillation achieving a more efficient energy transmission.

The alternating current is the energy that we receive in our homes, it is generated in the power plants by means of alternators.

The intensity of this type of current varies with time, and changes direction 50 times throughsecond (50hz). The generated voltage changes in the form of sine wave so it is not constant.

In the image:

1. Current by pulsations.
2. Direct current (DC).
3. Alternating current (AC).
4. Variable current.

IEC connector is the common name for a set of thirteen power connectors (called the connector specifications) and thirteen outlet panels (called input) specification defined by IEC 60320 (formerly IEC 320) of the International Electrotechnical Commission ( IEC). When used without other qualifiers, "IEC connector" usually refers specifically to the C13 and C14 connectors.