There are two major parts to any power supply

I suppose it is very obvious that any power supply has one input and one or more outputs. In the US, major appliance power suppliers accommodate for both 110 and 220 volts. Commercial power supplies (depending how much you are willing to pay) also accommodate for variable input and fixed or variable outputs. On a cautious note, newer power supplies automatically detect if the input is 110 or 220 volts. But there are still power supplies that one has to manually select one or another. Most recently, I have seen manual selection of input voltage in desktop computers.