Real basic explanation
In europe the standard voltage is 240v at 50 hertz. This means that one line of the outlet is 240v give or take a few volts depending on were the line is tapped at the transformer and how far the outlet is from the xfrmr. There is also a neutral (sometimes called a return line) plus a ground line to allow free electons to return to the earth, where they really want to be. A step down xfrmr is used to take this 240v single line down to us voltage of 110v. But it dosen't do anything to the frequency (hertz) of the current in the line which is why US motors run slower in europe. washing machines, blenders, etc.
In the US we use 110v at 60 hz. This means that one line of an an outlet is 110v plus or minus a few volts for the same reasons as above.
In a US 220v plug there are 2 lines that carry 110v (not really but close enough)when you add them together you actually get about 208v (because of a crossover point). which is why there are 2 breakers in your electrical panel for a 220v outlet.
depending on how many prongs there are on the 220v outlet determines how easy or dangerous it is to convert that outlet to 2 110v circuits.
if there are 4 prongs it is super easy.
if there are 3 it is a little more dangerous.

While i am not going to go into detail here, if you really need to do this let me know and I will try to talk you through the process.