Physical versus cash-settled futures

Settlement is the act of consummating the contract, and can be done in one of two ways, as specified per type of futures contract:
Physical delivery - the amount specified of the underlying asset of the contract is delivered by the seller of the contract to the exchange, and by the exchange to the buyers of the contract. Physical delivery is common with commodities and bonds. In practice, it occurs only on a minority of contracts. Most are cancelled out by purchasing a covering position - that is, buying a contract to cancel out an earlier sale (covering a short), or selling a contract to liquidate an earlier purchase (covering a long). The Nymex crude futures contract uses this method of settlement upon expiration
Cash settlement - a cash payment is made based on the underlying reference rate, such as a short term interest rate index such as Euribor, or the closing value of a stock market index. The parties settle by paying/receiving the loss/gain related to the contract in cash when the contract expires.[5] Cash settled futures are those that, as a practical matter, could not be settled by delivery of the referenced item - i.e. how would one deliver an index? A futures contract might also opt to settle against an index based on trade in a related spot market. ICE Brent futures use this method.
Expiry (or Expiration in the U.S.) is the time and the day that a particular delivery month of a futures contract stops trading, as well as the final settlement price for that contract. For many equity index and interest rate futures contracts (as well as for most equity options), this happens on the third Friday of certain trading months. On this day the t+1 futures contract becomes the t futures contract. For example, for most CME and CBOT contracts, at the expiration of the December contract, the March futures become the nearest contract. This is an exciting time for arbitrage desks, which try to make quick profits during the short period (perhaps 30 minutes) during which the underlying cash price and the futures price sometimes struggle to converge. At this moment the futures and the underlying assets are extremely liquid and any disparity between an index and an underlying asset is quickly traded by arbitrageurs. At this moment also, the increase in volume is caused by traders rolling over positions to the next contract or, in the case of equity index futures, purchasing underlying components of those indexes to hedge against current index positions. On the expiry date, a European equity arbitrage trading desk in London or Frankfurt will see positions expire in as many as eight major markets almost every half an hour.