$621 trillion in derivatives. What on earth does it mean?

I am at a loss to understand fully what these statistics really mean but The Economist points out in its on line edition that the "notional amount of outstanding over-the-counter derivatives" are presently around $601 trillion. Interest contracts make up the bulk of this money, some $465 trillion.

While I am not really able to explain what this means in real terms, and anyone that can is welcome to do so, I do know that it is a lot of money. The Economist points out that another way of gauging this market's size is not notional but by gross market value which more accurately assesses the amounts at risk. This figure is put at $24 trillion; I don't know why the substantial difference.

I do not know enough about these financial instruments which are assets "derived" from another from what I understand, like interest rate swaps, or credit default swaps as the graphic shows. Credit default swaps are pretty self explanatory, it is people or groups of people betting on whether a creditor like someone paying a mortgage will default on it or not. But I can recognize a lot of money when I see it and the possible crisis that arises if anything goes wrong.  Like many other folks, I also am aware that the crisis of capitalism is acute and these figures are staggering.

No matter what it means in detail it cannot help reflect the incredible wealth that exists in society, wealth that has its source in the unpaid Labor of the working class. The activity of buying and selling such things is a parasitical activity and I can only imagine what use such wealth could be used for if owned and allocated collectively in a planned rational way.