In finance, a futures contract is a standardized contract between two parties to exchange a specified asset of standardized quantity and quality for a price agreed today (the futures price or the strike price) but with delivery occurring at a specified future date, the delivery date. The contracts are traded on a futures exchange. The party agreeing to buy the underlying asset in the future, the "buyer" of the contract, is said to be "long", and the party agreeing to sell the asset in the future, the "seller" of the contract, is said to be "short". The terminology reflects the expectations of the parties -- the buyer hopes the asset price is going to increase, while the seller hopes for a decrease. Note that the contract itself costs nothing to enter; the buy/sell terminology is a linguistic convenience reflecting the position each party is taking (long or short).
In many cases, the underlying asset to a futures contract may not be traditional "commodities" at all – that is, for financial futures, the underlying asset or item can be currencies, securities or financial instruments and intangible assets or referenced items such as stock indexes and interest rates.
While the futures contract specifies an exchange taking place in the future, the purpose of the futures exchange is to minimize the risk of default by either party. Thus the exchange requires both parties to put up an initial amount of cash, the margin. Additionally, since the futures price will generally change daily, the difference in the prior agreed-upon price and the daily futures price is settled daily also. The exchange will draw money out of one party's margin account and put it into the other's so that each party has the appropriate daily loss or profit. If the margin account goes below a certain value, then a margin call is made and the account owner must replenish the account. This process is known as marking to market. Thus on the delivery date, the amount exchanged is not