* AC (Alternating Current): The voltage constantly changes direction, going from positive to negative and back again. This change happens at a specific frequency (usually measured in Hertz or cycles per second).

* DC (Direct Current): The voltage flows in only one direction, remaining consistently positive or negative.

Key Differences:

* Direction of Flow: AC changes direction, DC doesn't.

* Average Voltage: AC voltage is often described by its "RMS" (Root Mean Square) value. This is the equivalent DC voltage that would produce the same amount of power. The RMS value is about 0.707 times the peak AC voltage.

* Applications: AC is primarily used for power distribution, while DC is used for electronics, batteries, and certain industrial applications.

In simpler terms:

Imagine AC like a wave going up and down, while DC is like a straight line. While they might have the same "height" at their peaks, they're fundamentally different in how they behave.

Important Note: 30 volts of AC can be more dangerous than 30 volts of DC under certain circumstances. This is because the peak voltage of AC can be higher than the RMS value, leading to a potentially larger shock.