Live working – Hand tools for use up to 1000 V AC (alternating current) and 1500 V DC (direct current).
[Wikipedia / Further explanation (Not available in English): de.wikipedia.org/wiki/Liste_der_DIN-VDE-Normen/Gruppe_6]

AC is the abbreviation for Alternating Current (German: Wechselstrom)
DC stands for Direct Current (German: Gleichstrom)

Alternating current (AC) changes polarity 50 times per second (= 50 Hertz or 50 Hz)