Obviously you are not a Destiny game player.

[quote=Zmerr]What kind of world?[/quote]Earth and her former colonies

[quote=Zmerr]What are the Guardians?[/quote]Humans, Exo (robots), & the Awoken (humans who were able to escape from the Darkness but were afflicted with it) who have the ability to harness the Light against the Darkness as a Hunter, Titan, or Warlock.

[quote=Zmerr]What is the Traveler like?[/quote]No one knows, it has been dead for a long time.

[quote=Zmerr]How did this change happen?[/quote] The Traveler came and advanced human life and technology.

[quote=Zmerr]What WAS the change?[/quote]Human life span tripled. Humans were capable of colonizing the moon and other planets in the solar system. Any advancement in technology. The creation of the Ghosts in the Travelers dying breath capable of reviving dead Guardians, even if the Guardian has been dead for a centuries.

[quote=Enalais]The Traveler is pretty much a god like being that saved humanity from something called the darkness[/quote]The Traveler came before the Darkness. The Traveler did not save humanity from the Darkness. The Traveler failed and died, then the vast majority of humanity was destroyed and all the colonies fell to the enemies of The Traveler.

[quote=Enalais]it's pretty much a planet, and the last human bastion is now surviving on it it[/quote]You got that wrong. The City is the final bastion of humanity. Located somewhere on Earth, the City was built and is located directly under the floating Traveler to take advantage of its protective shields. Nobody lives on the Traveler.

See any of these wikias on the game:
http://www.destinygamewiki.com/wiki/Destiny_Wiki
http://www.destinypedia.com/Main_Page
http://destiny.wikia.com/wiki/Destiny_Wiki