Every character in the world has some kind of background. Even the lowliest of NPC's have some kind of history to them, although for the most part you will never find out they are descended from the last king of the 5th T'ping dynasty (on their grandmothers side) or that they survived the infamous Guld Dare Massacre of '87.
For the most part this background & details are decoration, but, they can provide insight as to why a character is acting the way they are
These can apply to PC's as well as those they encounter.
Note: This Background & Details Kit is aimed as players and NPC's from a fantasy setting. Volume 2 will deal with Sci-Fi/Futuristic settings.