What is the difference between DC and AC?

The primary difference between DC and AC is the direction of current flow. In a DC circuit, all electron current flow is in one direction. In an AC circuit, current flows in one direction for part of the time, and in another direction for another part of the time. In the AC circuit, we'll see current flowing "back and forth" instead of the unidirectional current flow we find in a DC circuit.
DC is "Direct Current", and AC is "Alternating Current". In DC, the current flow is in one direction only. In AC, the current flow is constantly changing direction.

An example of DC is the output of a battery. An example of AC is the power present in a home electrical system.
The current whose magnitude and direction remains change called as alternating current.

The current whose magnitude and direction remain unchanged called as d.c. Current.