Compound symbols allows you to calculate and visualize (real-time charts) combinations of futures contracts. This is used in spread trading as well as other applications.

E.g.: The gold future quotes in USD. The trader's account is in EUR. In order to evaluate his profit or loss the trader needs to take into account the evolution of the EUR-USD. In order to do this he has made a compound symbol (Gold future divided by EUR-USD future). This compound symbol displays gold future in EUR.