All terms
Index
A number that summarises the performance of a defined group of stocks.
An index works like a thermometer for a market. It combines the prices of many stocks into a single number, for example all 40 members of the DAX.
An index provider decides which companies belong, using fixed rules such as size and trading volume. The line-up is reviewed and adjusted regularly.
You cannot invest in an index directly, but an ETF can replicate it. Example: the DAX level on its own says little. What matters is how it changes over time.