Re: What is the Pokemon World like in your fan fiction?
Well, not all of my fics use the same interpretation, but the main and most famous one is that used in The Quest for the Legends.
Basically, the Pokémon world is a kind of parallel dimension, close enough to ours ("the animal world") for a rift or portal between them to open from time to time, usually one-way from the animal world to the Pokémon world. Thus, as life evolved in the animal world, some of it would get into the Pokémon world.
The Pokémon, meanwhile, are an entirely different, independently evolved type of life form whose genes are not based on the DNA molecule. They had a nice ecosystem going already, but animal world plants and viruses managed to root themselves pretty firmly in the new world. Animals, however, were quickly wiped out by direct competition from the much more advanced and powerful Pokémon.
A group of humans got there a long while later and managed to figure out how to cooperate with the Pokémon by caring for young ones that would, in return, protect them from predators.
Later, Pokémon world scientists discovered how to force a portal between the two worlds to open, and they created a two-way one in a laboratory which was then used for hundreds of years of cultural blending between the Pokémon and animal world in which Pokémon world humans for example imported animals (better suited to human dietary needs than Pokémon and much easier to kill without a guilty conscience as they had long ago realized the intelligence of the Pokémon) to keep on farms and occasionally as pets. Pokémon were never brought to the animal world to any great extent.
Much later, the animal world was destroyed in nuclear war; the portal had been closed for good shortly before after a wave of refugees had fled to the Pokémon world.
The Pokémon world today is very Pokémon-centric - the technology that has been the most developed all has to do with Pokémon, while some of the animal world technology, while indeed having been shared, has not been developed much further. A lot of work is being done by Pokémon that have an easier time doing it (e.g. schools employ Porygon to go over tests fairly, intelligently and quickly). Pokémon training is governed by ten Agreements between humans and Pokémon.
When The Quest for the Legends is set, the principles of Pokémon language have been discovered and are taught in schools, allowing potential trainers to understand their Pokémon.