What is the meaning of spheres of human life?

Life here is very similar to that of earth and differs only as we comprehend it from our present standpoint.

For instance, life is varied as on earth, also, are the inhabitants in their traits of character, which are diffused in different ways to blend in harmony and not jar inharmoniously from want of sympathy. Thus, every sphere in heaven or earth has its variety and condition adapted to the wants of its inhabitants—each fundamental principle being of itself a sustaining power, which must come from the outer to strengthen the inner soul.