What is the difference between ‘shadow economy’ and ‘grey economy’?
Shadow economy is like the "black market." Things are done and they may or may not be legal, like having taxes paid from your salary or not. Grey economy is like a small business owner that is a crook. They are avoiding paying all the required taxes so they pay some of your salary in cash with no taxes withheld, and the other pay by check with taxes withheld.