Apart from monitoring the prices of individual stocks, investors are really interested in the stock market indices (also called indexes).
Indices are aggregated prices of different stocks where the movement of the index price is the net movements of the different components in it.
A very important index is the Dow Jones Industrial Average (DJIA). Other very popular indices are the US S&P 500, the German DAX 30 and the UK FTSE 100.
Indices measure the stock's market performance. Most market indices are market-cap weighted, which means that they are based on the total market capitalization of the components within it. Some, like the DJIA are price weighted. This means that a price-per-share value is calculated for each stock within the index and then they are averaged to form the value of the index.
