Basically, a load of rich people lent a load of money to poor people never likely to be able to pay them back.
Pre-crunch, rich people were getting better returns from these loans than from 'real' investment in business.
What made things worse and more complicated was that rich people channelled these loans through their ownership and control of banks and big business, and this was done on a global scale.
Because these banks and corporations were 'too big' to fail and would have caused upheaval for us all. Those of us on moderate incomes had to underwrite these loans to the poorest.
Not only did the rich want their money back, they also demanded the tidy interest they were making and to maintain the big bonuses for their henchmen in the City.
Not only have the rich faced down tax rises on their substantial wealth they have also continued to avoid paying any taxes due for this.
And this is where we are. Hopefully when voters fully appreciate how they have been shafted they will rebel against all this.