A $1.2 Quadrillion ...?

Hi everyone,

Current undergrad student here trying to understand a concept.

I was recently debating with my friends how much money there was in the entire planet earth, and to read upon it, I ended up here:

http://www.marketwatch.com/story/this-is-how-much…

My question is, how can the derivative industry be worth so much more than the aggregate value of all debt, income, market cap, funds, and global GDP (basically everything)? What does this $1.2 value truly represent - is it an reflection of the leverage involved in these deals?

Please help,