LEED (Leadership in Energy and Environmental Design) is a rating system developed by the US Green Building Council to evaluate the environmental performance of buildings. Buildings can be rated LEED certified, silver, gold or platinum based on their performance in five categories - sustainable sites, water efficiency, energy and atmosphere, material and resources, and indoor environmental quality. The document provides examples of DePaul University and Ohio State University achieving LEED certification through practices like controlling pollution, reducing water usage, utilizing renewable energy and green power, reusing materials, and promoting natural lighting.