A kid goes to his dad and asks the meaning of the words "theoretically" and "reality". His dad tells him to go and look up the dictionary. The kid says he did that and he still couldn't understand it.
So the dad says to the kid OK son lets try and see if I can make it easy for you to understand the meaning of these words. He tells the boy to go and ask his mum if she would sleep with the man down the road for a million pounds. The boy runs back and tells the dad the mum would sleep with the man for a million pounds.
The dad then asks the boy to go and ask his sister if she would sleep with the boy next door for 2 million pounds. The boy goes to the sister and comes back to tell the dad that she would of course sleep with the boy next door for 2 million pounds.
the dad says, that's it then "theoretically we got 3 million pounds in reality we got a couple of slappers".