A market is a $ tradable instrument. An index is only an indicator and cannot be traded . In the USA the have both ie nasdaq index and a nasdaq tradable instument ( just like a share).
In the UK, we don't have that (as far as I know). Instead, we spread bet on the value of the index, or enter into a CFD on an index.
What puzzles me intensely is this:-
How come the QQQ instrument which is EXACTACLY one fortieth of the NAS index,mirrors the shape of the NAS exactly?
8th wonder of the world?