"Let's look at the etymology: 'permanent' is a Latin word meaning to endure or to persist throughout, and 'culture' is any of those activities that support and distinguish human communities. Probably the easiest way to understand it is through subsets of words like 'agriculture.' When I say the word 'agriculture,' you think, oh, that is the activity which produces food for the community - and you would be wrong. Agriculture is that activity that produces commodities for the international market."
See What is Permaculture?
Also see Permaculture.Net