Exchange

A centralised marketplace with a membership, a rulebook and a published price. Interest arrives as orders, is sorted into an order book by price and then by time, and is paired by a matching engine that applies the venue's stated priority rules to everyone alike. The prices it produces are the reference prices for the instruments it lists, which is why an exchange price is the thing other markets quote against.

Not every market has one. Shares and listed futures are exchange traded; currencies are not, and deal over the counter between counterparties instead, which is why a currency pair has no single official close and no home venue. The distinction decides several things a reader meets daily: whether trading hours are set by a venue's calendar, whether an opening and closing auction exists, and whether a halt can stop the market for everyone at once.

A contract for difference written on a listed instrument references the exchange price and is not itself traded on the exchange. Nothing reaches the venue when such a contract is opened: the transaction is between the two parties to the contract, the listed company holds no record of it, and the exchange's rules reach the position only through the price it references and the hours during which that price exists.