Permaculture is a branch of ecological design, ecological engineering, and environmental design that develops sustainable architecture and self-maintained agricultural systems modeled from natural ecosystems. The term permaculture (as a systematic method) was first coined by Australians Bill Mollison and David Holmgren in 1978. The word permaculture originally referred to "permanent agriculture"  but was expanded to stand also for "permanent culture," as it was seen that social aspects were integral to a truly sustainable system as inspired by Masanobu Fukuoka's natural farming philosophy.
"Permaculture is a philosophy of working with, rather than against nature; of protracted and thoughtful observation rather than protracted and thoughtless labor; and of looking at plants and animals in all their functions, rather than treating any area as a single product system." - Bill Mollison 
PatternsPermaculture is a design philosophy which seeks to exploit and imitate naturally occurring patterns. Patterns occur in nature in many forms: From studying Fractals, patterns emerge as mathematical principles from apparently random things such as the shape of plants.
Permaculture designers are encouraged to develop a sensitivity to the patterns that exist in nature, to determine their complex functions and the various interrelations. Since humans have complex intentions and a wide variety of goals, permaculture design draws upon a variety patterns, building a pattern language as defined by Christopher Alexander. These natural patterns can often be utilized—either exploited or imitated or both exploited and imitated—to satisfy specific design goals. For example, "the application of pattern on a design site involves the designer recognizing the shape and potential to fit these patterns or combinations of patterns comfortably onto the landscape".[full citation needed] Patterns such as spiral, branching, wave, net and honeycomb are structural patterns that are repeated throughout nature. "A lot of the structural patterns combine strength and beauty with efficiency of space through large surface area or extensive edges. Looking at the benefits of these characteristics provides us with attitudes that we can emulate in our design work."
... more: http://en.wikipedia.org/wiki/Permaculture