How do ac and DC voltages work?

the currents move back and forth ( alternating current) when something is plugged into a socket, the ac voltage (120 v) is moved to the device.

then there is dc voltage, dc voltage works with electricity flowing straight to a device, it does not alternate. just as a battery hooked up to a wire, connected to a switch, connected to a light, connected to the battery again.

ac could connect to the light from the switch , from the battery.