Whilst every publicly traded company lists stocks on the financial markets, some, such as large multi-national corporations, list different version of their stocks on different indices.
So for example, let’s examine the Japanese company Toyota. The company’s stock can be bought on the Nikkei (T7203) and in this example has a current stock value of 8377.0 Yen. Toyota shares are also available in Frankfurt, London and New York, with the price linked to the one on the Nikkei. This means that when the Nikkei is closed, it is still possible to trade Toyota stocks in the other markets across the world. This encourages global trading, as it allows a British trader for example to trade the markets directly, rather than being reliant upon an automated trade or having to trade the Nikkei in the middle of the night.
In examples like this where companies list their stock on various exchanges, brokerages are able to offer an ADR - Average Daily Rate - which is a version of the stock that can be traded, taking into account all of the varying listings of the firm’s stock across the globe.