Here's why:

* Direct Current (DC): Charges flow in a single, consistent direction. Think of a battery powering a device.

* Alternating Current (AC): The direction of charge flow reverses periodically. This is how electricity is delivered to homes and businesses.

The constant shifting of charge direction in AC creates a cyclical pattern, which is why it's often represented as a sine wave. This oscillation is what makes AC particularly useful for power generation and transmission.