The basic premise behind this type of fraud is money. The promise of lots of money. Nigerian Scam and Advanced Fee Fraud are basically one and the same type of fraud. The basic premise behind these types of fraud is that in order for you to get your "promised" money you have to send earnest money up front to show your good faith.
Sadly, by the time the victim of these types of fraud realize that they have neither won nor been given any of the promised money they have sent hundreds if not thousands of their own dollars to another person who lives in another country.
There are hundreds if not thousands of different types of letters being sent to unsuspecting victims worldwide. Click on the following link to see a sample of the type of letter being sent everyday.