Transwarp conduits are the subspace corridors the Borg use to move vessels across thousands of light-years in minutes, linked through hubs scattered around the galaxy.
A transwarp conduit is a tunnel-like passage through subspace that a Borg ship can enter and travel along at speeds far beyond conventional warp. The Collective maintained a vast network of these conduits, with major junctions anchored at transwarp hubs, allowing cubes to appear deep inside other civilizations' territory with warning.
Renegade Borg under Lore used a conduit during their attacks on the Federation. Voyager's crew later stole a transwarp coil from a Borg sphere, which shortened the ship's journey home considerably before it burned out. With help from an admiral from the future, Voyager eventually used a conduit to reach the Alpha Quadrant and destroyed a major hub.