AC vs. DC
AC - Alternating Current
Alternating current refers to current that changes direction. If you could watch electrons being moved by an alternating current in a wire you would see them bouncing back and forth. Alternating Current is always associated with a frequency, that frequency is how often the direction of current changes. For example, household electricity in the United States is an alternating current that switches direction at a rate of 60 hertz (Hz) or 60 times per second. Different locations have different standards for the frequency of the electricity they use, but most power is used at 50 or 60 Hertz.<ref> http://en.wikipedia.org/wiki/Alternating_current </ref>
DC - Direct Current
Direct Current is much simpler. It is a current that does not change direction, instead it keeps electrons constantly flowing in the same direction.