What is the difference between Power Sources AC and DC?

Answer 1

AC (alternating current) constantly switches between positive and negative between the two wires. DC (Direct Current) always has one wire at positive and the other at negative, with no switching.

DC is better for smaller applications such as home electronics as it is easier to work with.

AC is often used in either audio applications, or in the power who comes from the outlets in youre house. as it travels a much longer distance, with less power loss.

Answer 2

Alternating Current (AC)
Direct Current (DC)
DC is consistent. 12 VDC is just that and has Negative and Positive like a car battery.
AC is changing constantly from Negative to Positive. In a House the 115 VAC actually Peaks at around 168 Volts if I remember correct, it goes to 168 Positive then drops through 0 to 168 Negative. The 115 Volts is what is known as "Average Voltage".
Knowing this you can plug an electric fan into DC in both directions +/- then -/+ and it will spin in different directions. Plug an electric fan into AC changing the wires and it will still spin in one direction.