Indicators are presentations of measurements. They are bits of information that summarize the characteristics of systems or highlight what is happening in a system.
Indicators simplify complex phenomena, and make it possible to gauge the general status of a system.
You can find indicators everywhere, from the gauges and dials on a car's dashboard, to readings taken by a doctor, to the financial reports in the business pages of a newspaper. Indicators make it easier to communicate about sustainable development. They translate the concept of sustainable development into numerical terms, descriptive measures, and action-oriented signs and signals. An index can itself be used as an indicator, one that greatly simplifies the complex information contained in all of the index's constituent parts. Measures and indicators of sustainability are set apart by the way they combine social, economic and environmental trends, and by the way they illustrate the links between and among systems.