In this country, most generated electricity is 60 Hertz AC. I think some hydroelectric plants, like the Tennessee Valley Authority, used a lower frequency, something like 25 Hz. A lot of other countries use 50 Hz. A lot of aircraft systems use 400 Hz. There at one time was intense competition between Edison and Tesla over which was better for power distribution, AC or DC. Edison won. If I recall my Industrial Electricity classes from the 1960s, DC can be transmitted over distances with a lower loss factor, but changes in Voltage are easier with AC. To change something like a 2200 Volt power line to 120 V for house distribution, DC would back then need some form of motor generator type system with attended mechanical wear, while AC needs just a simple transformer with no moving parts.