What's the difference between AC and DC? Don't laugh.

Alternating current is alternating current, and its amplitude, direction and frequency can be changed. What we usually call alternating current refers to industrial and domestic electricity, the frequency is constant at 50 Hz, and its amplitude is sinusoidal.

Direct current is direct current, and the direction of current will never change.

Ask if you don't understand. No kidding. I don't know how old you are this year. If you want to know more, I suggest reading high school textbooks, talking about alternating current or the place where alternating current is generated, and carefully looking at the essential differences between alternating current and direct current will be more helpful to understand this problem.