The difference between ‘Potentially’ and ‘Realistically’

‘Dad, what is the difference between ‘Potentially’ and ‘Realistically’?’

The father thought for a moment, then answered,
‘Go ask your mother if she would sleep with Brad Pitt for a million
dollars .

Then ask your sister if she would sleep with Brad Pitt for a million
dollars,

and then, ask your brother if he’d sleep with Brad Pitt for a million
dollars.

Come back and tell me what you learn from that.’

So the boy went to his mother and asked, ‘Would you sleep with Brad
Pitt for a million dollars ?’

The mother replied, ‘Of course, I would! We could really use that
money to fix up the house and send you kids to a great university!’

The boy then went to his sister and asked, ‘Would you sleep with Brad
Pitt for a million dollars?’

The girl replied, ‘Oh good heavens! I LOVE Brad Pitt and I would
sleep with him in a heartbeat. Are you nuts?’

The boy then went to his brother and asked, ‘Would you sleep with
Brad Pitt for a million dollars?’

‘Of course,’ the brother replied. ‘Do you know how much a million
bucks would buy?’

The boy pondered the answers for a few days and then went back to his
dad.

His father asked him, ‘Did you find out the difference between
‘potentially’ and ‘realistically’?’