There are many people who ask about what permaculture is and there are also many different answers, depending on who you ask and where in the world they are coming from. So it is not easy to tell what is permaculture, but there is a natural explanation in the following.
Permaculture is a copy of the nature that is at the place where you make a permaculture project, so permaculture is different from place to place. However, it is always about making a permaculture design, that utilizes all the natural factors in the place where the permaculture project is made, in the most optimal way. Therefore, there are many different answers to question! What is permaculture?
My short answer is - "From Earth to Table to Earth using only nature."
There are 3 ethical principles and 12 principles or rules that apply everywhere. My Danish answer to what is permaculture, is a kind of definition.
Permaculture is to live on and work the land for agriculture on farms and gardens, in close cooperation with nature. So, everything always is a part of nature's biological cycle, to the benefits people and the whole society.
In other words, open to nature wherever and whenever it is possible, use only natural biological methods, no waste, no chemicals, no people who do not get a reasonable return on their efforts. Permaculture is about creating a copy of the original nature with so many food-productive animals and plants as possible.
In a permaculture project, animals, plants, insects, and microorganisms must be symbiotic elements in nature's total biological circle. Permaculture design is about how to put together the soil, water, animals, plants, insects- and microorganisms in a biological cycle in the most optimal and productive way.
There is also a longer answer including a little history:
The 12 principles show that nature is complex and therefore permaculture is complex, no plants or animals can stand alone, every living animal or plant is living in a symbiosis with other animals and plants. Permaculture is about giving nature the opportunity to create productive biotopes. Permaculture aims to recreate the natural interplay between soil, water, plants, and animals.
It can also be seen that a large part of the 12 principles will work by themselves if you stay within natures biological cycle and only use the opportunities that appear from nature and allow it to take the time needed.
Nature produces no waste, only new products. So whatever you find in nature there are several uses. Some might have heard of a slogan saying, "From Earth to Table". With permaculture it's only halfway, here a similar slogan would be, "From Earth to Table to Earth" it's always about closing the biological cycle
We must live in nature's biological cycle. A permaculture project must consist of people, plants, and animals that are bound together in a biologically optimal way, that recreates nature's biological cycle. All items (plants, animals, buildings, etc. must have 3 or more functions.
Several crops are grown in a mix, in the same area: trees, fruit trees (large and small) berry bushes, herbs, root plants, mushrooms. It must be perennial crops and annual crops. 7-9 productive layers of the plants in the same area. Grown in companion planting system so that all plants have the benefit of each other. In addition, livestock and everything nature have to offer like microorganisms, insects, birds and other animals.
Nature works by itself. Nature's biological cycle operate year after year all by itself, it is the normal mode of nature. Every time we spray, plow or whatever stupidities we come up with, we put the nature back to year zero. It's year zero (an empty field) that's the most unstable and the least productive with the highest costs.With permaculture, it is about creating permanent growth of food-producing plants and animals in cooperation with nature.
Many books are written on permaculture, Bill Mollison and David Holmgren, who are the founders of permaculture, wrote the book "Permaculture One: A Perennial Agriculture for Human Settlements" which is a rewriting of Holmgren's university thesis. Permaculture One is the book that began the permaculture movement worldwide. Bill Mollison followed up with, Permaculture Two, that is developing the permaculture ideas even more.
Finally, in 1988, Bill Mollison writes the book, "Permaculture: A Designers' Manual" It is a handbook for teaching and is the book used as a textbook for all Permaculture Design Certificate (PDC) Courses. The book is very extensive and not easily readable, as the name says it is a handbook. The book consists of 14 chapters, to read the book from start to finish will not make much sense to many, it is a manual. But to understand what each chapter is about is important.
The first 4 chapters of the book I recommend that everyone reads and understand no matter how long it takes. Especially Chapter 4 "Pattern Understanding" is fundamental for understanding permaculture. The rest of the book is based on chapter 2, 3 and 4.
There are many other books that are of great importance to my understanding of permaculture. Here I will only mention two that I have been very happy to read.
Masanobu Fukuoka's book The One-Straw Revolution, 1975.
Smith J Russell, Tree Crops, A Permanent Agriculture of 1929.
There many other more recent books, Toby Hemenway, Gaia's Garden is a book I have noticed, and David Holmgren has done much good work since Permaculture One. Permaculture: Principles and Pathways Beyond Sustainability, are another milestones from Holmgren.
Most permaculture experts now have websites and all material is easily accessible. Geoff Lawton has been working on the internet for many years and has made countless very good educational videos about permaculture, Establishing A Food Forest, Permaculture Soils, Harvesting Water, Permaculture Design and the 2015 online PDC is just some of the videos I have. Larry Korn is on the internet with online teaching and resently published a new edition of Masanobu Fukuoka's book The One-Straw Revolution.