A zero-width gateway through space that connects two places. Travel is instantaneous and anyone using one will cross hundreds of light years in an instant. They were an invention by CST co-owners Nigel Sheldon and Ozzie Fernandez Isaacs. Sheldon and Issacs linked the first wormhole between Earth and Mars, and met the 1st InterSolar Mars exploration team from Earth, that had been sent into space long before.
The Commonwealth uses trains to travel from planet to planet. The wormholes are covered by pressure curtains that stop the atmospheres of the connecting planets mixing. Once the trains pass through the pressure curtain to the destination planet, the new atmosphere is fed into the compartments like a decompression chamber for divers to allow the passengers the time to get used to the new atmosphere.
The wormholes are also used for exploration, using them to survey new possible colonies - there is a CST exploration on Merredin.
The starship Second Chance used a continuous wormhole drive for FTL travel, something Ozzie Isaacs claimed was "hyperspace," something he worked to avoid in the first prototype wormhole, indicating there are several separate methods of wormhole travel.
Quantum fluctuations are consistent with wormhole activities and create a great deal of gravitational distortion as a side effect.