Jita is located in the Kimotoro constellation of the Forge region. With arround 1000 Pilots on average, and up to about 1500 Pilots at weekends, Jita is by far the crowdiest place in New Eden. Since several high level agents conducted their business from the system's stations many of the pod pilots started to trade at the Caldari Navy Assembly Plant orbiting the fourth Moon of the fourth planet. The facts that Jita is nearly in the Center of the other Trade Hubs in Empire (Amarr, Rens, Dodixie and Hek), close to 4 other regions (for price comparison) and near most of the Caldari starting Points are also helping in populating this System.
Due to its High population Jita is a very vulnerable system when it comes to lag issues. All of Jita's Asteroid Belts (it used to have 8 Asteroid Belts and 3 Ice Fields) as well as the - at that time - busiest Gate (to Kisogo) have been permanently removed from the System in order to help removing the lag, or at least getting it down to acceptable levels. Jita is currently one of the 5 Systems in EVE that runs on its own dedicated Server Hardware.
The current volume of trade conducted in Jita totals several billion ISK a day, more than all other Trade Hubs combined.