-No this isn't the band singing "Highway to Hell" but types of current to know about. Your power supply in your computer has the job of converting AC to DC current. This is much like you car which has a alternator. The alternator makes AC current and changes it over to DC to charge the batter and fire those spark plugs. In electronics we make good use of DC current since its predictable as electricity will get.
AC Current- this is called Alternating Current and is found mostly in your household and for high voltage applications. The current moves back and forth over a wire 60 times a second. The voltage will change from a Positive charge to negative charge rapidly.
DC Current- this is called Direct Current and will run from a negative to positive in one direction. The current runs in one direction only and measured predictably from negative to positive every time. The DC current is most dominant in a low voltage system such as a PC.