In a nut shell, a Permaculture is a culture designed to be permanent. Typically a Permaculture design is when you set up a garden of eden or food forest. Where everything compliments each other and works together for sustainability. Terms like wild craft and nature crafting are parts of this system. An example would be setting up a fish tank where everything in the tank works together to make your job easier and to offer a more natural habitat for those living in the tank. A Permaculture is setting up your property to do such a thing. Companion planting and things of this nature.
On a more specific level: a Permaculture is where you set up a permanent society that uses sustainable practices.