The Index consists of liquid United States dollar-denominated, high yield corporate bonds for sale in the United States, as determined by International Index Company Limited. HTG is based in Boston, MA.
In direct current (DC), the electric charge (current) only flows in one direction. Electric charge in alternating current (AC), on the other hand, changes direction periodically. The voltage in AC circuits also periodically reverses because the current changes direction. Most of the digital electronics that you build will use DC.
Also See: Diodes | Power Supplies. AC means Alternating Current and DC means Direct Current. AC and DC are also used when referring to voltages and electrical signals which are not currents! For example: a 12V AC power supply has an alternating voltage (which will make an alternating current flow).