“The locations to a lot of systems were lost before wormhole stabilizing tech was developed, but researchers find them sometimes in reconstructed data troves.“ (Network Effect)
Wormholes are structures linking far-off points in space, and can be traveled using space transports to cover distances faster than would be possible otherwise.
Wormhole travel can only be done if the ship's engines have a wormhole drive. Each wormhole seems to connect only to specific points, so a long voyage may require travel through multiple wormholes. Colonizing a planet that is not near a wormhole would require long voyages (e.g. hundreds of years) with colonists in 'cold sleep' (cryogenic stasis).
In the Corporation Rim, the coordinates for wormhole travel are proprietary and are sometimes lost if a corporation goes bankrupt or destroys its data archives while resisting a hostile takeover.