Emerson discusses the harmony and unity between man and nature throughout this essay. He believes that the world is divided into two parts: the self (the soul) and the outside world (which he refers to as "nature"). He discusses the relationship between the two parts and explains that there can be perfection between the two parts. If this perfection exists, then the self can communicate with the outside world, which he terms "community." This is a very spiritual essay, and the following link goes into a lot more detail for you.
The essay is divided into eight parts/chapters: Nature, Commodity, Beauty, Language, Discipline, Idealism, Spirit and Prospects.