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AC/DC and the Difference Summarized
So there it is. Kind of.
Direct Current flows in one direction. It's advantages are that it is a constant, reliable and basic form of energy. It's main disadvantage is that it dissipates over length, which makes it dangerous and difficult to use for distribution.
Alternating Current flows in both directions in a sinusoidal wave. It's main advantage is that it is more versatile than direct current, and more reasonable for distribution. It's disadvantages include the fact that it does not maintain a constant current, and can cause unwanted vibrations, as well as electrostatic and magnetic fields; all of which interfere with maximum power transfer and the quality of the current. That means that there are more components necessary to make it efficient and reliable.
That is really what the difference is. To get a better understanding of how AC is made more constant and reliable make sure to learn about the difference between single-phase and three-phase sources, and learn about what inductors and capacitors do here.