What is Alternative Current and Direct Current?

Alternative Current (AC)

Alternating current (AC) is an electric current which periodically reverses direction, in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. A common source of DC power is a battery cell in a flashlight. The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.
In figure the green line is showing the flow of Alternative Current. Alternative Current is flowing in different directions such ups and down directions.

Direct Current (DC)

Direct current (DC) is the unidirectional flow of an electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams.
In above figure the red line is showing the flow of Direct Current. Direct Current is flowing in straight direction such as one direct.

Difference between AC & DC

As you know that AC stands for Alternative Current where as DC stands for Direct Current.
Alternative Current flows in ups and down directions but Direct Current flows in straight direction

Alternative Current can't be store but Direct Current can be store for future use.
In Pakistan we show Alternative Current by P & N, P means Phase and N means Neutral. And for Direct Current we show +ve & -ve , +ve means Phase and -ve means Neutral.
The most useful examples of Alternative Current use in home electricity, home motors
And the most useful examples of Direct Current use electrical store able batteries,  Mobile phone batteries, motor vehicles batteries, etc