Derivatives are financial contracts, whose values are derived from the value of something else (known as the underlying). The underlying on which a derivative is based can be an asset (e.g.,commodities, equities, stocks, residential mortgages, commercial real estate, loans, bonds).

Derivatives can be used to mitigate the risk of economic loss arising from changes in the value of the underlying. This activity is known as hedging. Alternatively, derivatives can be used by investors to increase the profit arising if the value of the underlying moves in the direction they expect. This activity is known as speculation.

Hedging

Derivatives allow risk about the value of the underlying asset to be transferred from one party to another. For example, a wheatfarmer and a miller could sign a futures contract to exchange a specified amount of cash for a specified amount of wheat in the future. Both parties have reduced a future risk: for the wheat farmer, the uncertainty of the price, and for the miller, the availability of wheat. However, there is still the risk that no wheat will be available due to causes unspecified by the contract, like the weather, or that one party will renege on the contract.

From another perspective, the farmer and the miller both reduce a risk and acquire a risk when they sign the futures contract: The farmer reduces the risk that the price of wheat will fall below the price specified in the contract and acquires the risk that the price of wheat will rise above the price specified in the contract (thereby losing additional income that he could have earned). The miller, on the other hand, acquires the risk that the price of wheat will fall below the price specified in the contract (thereby paying more in the future than he otherwise would) and reduces the risk that the price of wheat will rise above the price specified in the contract. In this sense, one party is the insurer (risk taker) for one type of risk, and the counterparty is the insurer (risk taker) for another type of risk.

Derivatives massively leverage (leverage is borrowing money to supplement existing funds for investment in such a way that the potential positive or negative outcome is magnified) debt in an economy, making it ever more difficult for the underlying real economy to service its debt obligations and curtailing real economic activity, which can cause a recession or even depression

Derivatives typically have a large notional value. As such, there is the danger that their use could result in losses that the investor would be unable to compensate for. The possibility that this could lead to a chain reaction ensuing in an economic crisis, has been pointed out by legendary investor Warren Buffett. He called them 'financial weapons of mass destruction.' The problem with derivatives is that they control an increasingly larger notional amount of assets and this may lead to distortions in the real capital and equities markets. Investors begin to look at the derivatives markets to make a decision to buy or sell securities and so what was originally meant to be a market to transfer risk now becomes a leading indicator.

See also Wikipedia:   Derivatives