A typical currency futures contract is "FUT-USDINR-27-Dec-2013"; wherein FUT implies the futures contract, USDINR are the underlying assets for the contract and the specified date 27th December'2013 is the expiry date for the stated contract.
Generally, currency future contracts bear different expiry term and expire post the completion of the tenure. More precisely, the currency future contract expire before two days of the last working day/ trading day of the exchange of the pre-specified expiry month.
Trading in the currency futures can be executed with a smaller margin and not with the whole amount for the transaction. This way, currency futures trading allows you to leverage on your limit. But simultaneously your risk exposure increases.
So, if the currency fluctuates in your favour i.e. rises in case you hold a buy position or decreases in the event if you hold a sell position, you generate profit from trading in currency future derivative else loss. Settlement in the trade like in equity trading is made in cash.