The Navigators' Guild was in operation around 5,000 BBY, at a time when hyperspace explorers were blazing new trails for the growing Galactic Republic. Scouts across the galaxy were attempting to discover new hyperspace routes, and the Navigators Guild rewarded them for that information. Once the existence of a new route has been reported, the process of verifying the safety of the route began, and the guild invested large amounts of resources and time to make sure that the route was safe and would remain in existence for the long-term. Once a lane has been verified, the Hyperspace Navigators Guild passed the data on the route on to the Space Ministry, from which point the coordinates were distributed throughout the galaxy.
Although the need for the Guild diminished with time, it was still operating during the era of the New Jedi Order, at which time it remained one of the best sources for new hyperspace routes, especially in the Deep Core, Wild Space, and the fringes of the Unknown Regions - areas ignored by the Space Ministry.