Overview
Kobol is said to be the original home of mankind, once shared with the Lords of Kobol.
Kobol is a verdant world of seas and continents, the latter having large swaythes of woodland, grassland and forests (Kobol's Last Gleaming Part I).
Kobl was a place where humans and the god dwelt in harmony, the seat of power being the City of the Gods, itself dominated by the Forum and Opera House (Kobol's Last Gleaming Part I).
Great Exodus
The Great Exodus from Kobol took place some 2,000 years prior to the events of the new Battestar Galactica. At that time, the 12 tribes departed Kobol for the Cyrannus system (Video Game).
It is unclear whether the gods themselves departed Kobol at this time. However, given their presence is not seen amoung the 12 colonies, it is possible they remained on Kobol. This may be the reason why not everyone departed Kobol at the time of the Great Exodus.
Certainly, it is known that the Thirteen Tribe departed Kobol some time after the main exodus (Mini-Series), to seek a planet known as "(Earth)". The gods may also have abandoned Kobol at this time to travel with the Thirteenth Tribe.
More to be added