It means Volts Alternating Current. AC is what comes out of power sockets in your house. Im not a 100 percent sure but I believe most if not all of Europe uses 220V. Hope that helps :)
The voltage isn't intended to match exactly. The voltage from the wall varies by 10% anyway - ie. "230" means 207 ~ 253 volts. Almost every country in the world uses either "two hundred and something volts" or "one hundred and something volts", so that's why there are two versions of this amp.
(https://en.wikipedia.org/wiki/Mains_electricity#Voltage_levels)
I'm using the 220 volt version in NZ with 230 volt mains power.
So it's good that you checked, but don't worry!