From the creator:
A companion booklet, The Magical Land, contains background information and educated guesses to suggest ways of filling in certain blanks. It explores pony physiology, useful historical parallels from the real world, and possible technological and societal connections that might not be obvious.
The Magical Land looks at what is known of Equestria as seen in My Little Pony: Friendship is Magic, and discusses the implications some of the items and technology seen, and how the world seems to work. It does not provide concrete answers, and is a stepping off point for personal world-building.