Most people think they understand both what a bank is and what money is.
Most people are wrong.
Taking the UK and USA as examples, it is assumed that the Bank of England and the Fed in the USA are, in some way, parts of the government; or at very least that they are controlled by politicians.
Banks are private institutions designed as corporations, to make money. The control of money by banks (and only they ultimately control money) is for the interests of the banks and finance houses. In essence they rent money to governments and individuals. The money rented is always a debt that has to be repaid. The rental is always a debt that has to be repaid. No money comes into the system without this double debt.
This is the fundamental reason the world is drowning in debt.
If you think banks lend depositors money out again, that is a complete misconception.
If you think most money looks like this, that is a complete misconception.
Most money is created out of 'thin air' and pixels, on computers. This is called leveraging. The money - as in the picture above - represents just 3% of all money. (You may need to read that last sentence again.)
Many economists and most politicians have little real grasp of what money actually is and how the banks use debt to wield huge power.
Without an understanding of money and banks it is hard to grasp what is happening to Greece.
A very good site that is worth spending time exploring is positivemoney.org