The charter for the UCLA Sustainability Committee defines sustainability as: “the physical development and institutional operating practices that meet the needs of present users without compromising the ability of future generations to meet their own needs, particularly with regard to use and waste of natural resources. Sustainable practices support ecological, human, and economic health and vitality. Sustainability presumes that resources are finite, and should be used conservatively and wisely with a view to long-term priorities and consequences of the ways in which resources are used.” This definition is certainly useful for bigger corporations, but what does sustainability mean for just one person? In very broad terms, it refers to living in such a way that does not have a negative impact on the earth's ecosystems.
Living in a sustainable manner is important because it ensures that there will be a planet to live on for future generations. Many estimates put a date on the "point of no return" being somewhere in the 2030s, if governments don't switch to renewable energy sources within that time period.