A stock will have a single "primary" exchange. This is where the stock is "listed" (apple is listed at NASDAQ, for instance). However a stock may be traded at

A stock will have a single "primary" exchange. This is where the stock is "listed" (apple is listed at NASDAQ, for instance). However a stock may be traded at multiple exchanges (BATS, NYSE, NASDAQ, DirectEdge, etc) as well as other market centers. Hope that helps...