AC and DC dual-use means that it can be either AC power supply or DC power supply.
AC means AC power, while DC means DC power.
The full name of AC current is Alternating Current, which means that the current direction changes periodically with time. The average value of operation in a cycle is zero. The full name of DC current is Direct Current, also known as "constant current". Constant current is a kind of DC current, which has the same size and direction. When transmitting the same power, the wire used for DC transmission is only 2/3~1/2 of that for AC transmission.