Criteria are a set of values that characterize forest condition.
Indicators are measurable attributes or aspects of criteria. Repeated measurement of indicators can be used to describe trends and chart change over time. The 1992 Rio Earth Summit recognized the importance of forests to sustainable development when world leaders adopted the Statement of Forest Principles and Agenda 21 an international action plan. Governments and non-government organizations acknowledged the need to develop a common understanding of what is meant by sustainable forest management and how to achieve it. Its first meeting took place in 1994 in Geneva, Switzerland.