Agenda 21 is a non-binding action plan developed by the United Nations in 1992 during the Earth Summit in Rio de Janeiro. It aims to promote sustainable development globally by addressing environmental, social, and economic challenges. The plan encourages countries to create local strategies for sustainable growth, focusing on issues like poverty, health, and biodiversity. The document outlines various principles and recommendations for governments, businesses, and communities to follow. It emphasizes the importance of public participation and collaboration among different sectors to achieve sustainable development goals. While not legally binding, Agenda 21 serves as a framework for many countries to develop their own sustainability initiatives.