Wormholes are shortcuts in space, allowing many light years of travel in a few seconds. More scientific descriptions include :

by Enrico Rodrigo in 'The Physics of Stargates' as

a region of spacetime containing a "world tube" (the time evolution of a closed surface) that cannot be continuously deformed (shrunk) to a world line (the time evolution of a point or observer).

or by Matt Visser in 'Lorentzian Wormholes' as

If a Minkowski spacetime contains a compact region Ω, and if the topology of Ω is of the form Ω ~ S × Σ, where Σ is a three-manifold of the nontrivial topology, whose boundary has the topology of the form ∂Σ ~ S2, and if, furthermore, the hypersurfaces Σ are all spacelike, then the region Ω contains a quasi-permanent intrauniverse wormhole.

In the Imperial Concordant universe the ends of a wormhole connect distant points in space and cover many light years in a few seconds. Travel time to the wormhole is more than the time it takes to traverse the light years the wormhole connects. For example, the ring of sixty wormholes around Lutetia Star are six hundred million kilometres from the star (four hundred fifty million kilometres from Lutetia, one hundred million kilometres from outer Lutetia). To cover this distance from Lutetia, using standard acceleration of two metres per second squared, takes nearly eight days, and a similar amount of time to slow down on the other side. Sometimes several wormholes have to be traversed to get to a destination. As an example, going to Kokomo from Udara One means traversing the wormhole to Udara Seven, then to Lutetia, and then to Kokomo. Using the same constant acceleration, and depending on exactly where the planets are in their orbit, the time will take twenty two to twenty four days. Going from Kokomo to Alesia (the journey taken by Daisy, Kristi and Riya) will mean traversing the wormhole from Kokomo to Lutetia, then from Lutetia to Alesia. The journey will take about eighteen days.

The smallest wormholes in the Imperial Concordant universe are ten kilometres across. Smaller wormholes are used only for communication. The ten kilometre minimum is used to protect traversing spacecraft from gravitational tidal effects. If a spacecraft tries to traverse a wormhole too small for its size it will be torn apart by gravitational tides. For example, if a wormhole is only three hundred metres across, and a spacecraft over three hundred metres across tries to enter, the gravitational tides will tear it to atoms. The ten kilometre minimum gives a safety margin, and ships up to ten kilometres can traverse safely. Larger wormholes can, and are built, with one hundred kilometres being the most commonly built large size. Most are thirty five kilometres across, like all the wormholes at Lutetia and Udara One.