First of all, nobody knows how big the derivatives market is and no one knows how many dollars are at risk. Those involved in making the regulations are also the largest players in the market. Whatever "reform" is being worked out will benefit those who are part of the industry.
Here's how Wikipedia describes a derivative:
A derivative is a financial instrument which derives its value from the value of underlying entities such as an asset, index, or interest rate--it has no intrinsic value in itself. Derivative transactions include a variety of financial contracts, including structured debt obligations and deposits, swaps, futures, options, caps, floors, collars, forwards, and various combinations of these.