Don't worry, they are the same thing. The public 220/240 volt electricity supply fluctuates by 10% and this is just different ways of referring to the same voltage.

Obviously the US standard 110/120 volt system is completely different.

The one type of product which has a difficulty being used through a transformer between 110 and 220 volts is something which is speed dependent like a record player (I'm showing my age here) which will revolve at a different speed, not because of the voltage but because the a.c. frequency is different (50 hz on the 220 v supply, 60 hz on the 110 v supply). Changing voltage through a transformer is easy, changing frequency requires a substantial piece of equipment.