Hyperdrive is a system that allows a ship to enter a universe where the laws of physics allow it to travel at faster than light speeds, and as such is used as a propulsion system to cross interstellar distances by Known Space species. It can be used outside the singularity around a gravity well. A Quantum I Hyperdrive which is the most accessible rate, covers a distance of 1 LY in 3 days.
The sysem was perfected by the Outsiders, then sold to Puppeteers and later to Humans of the We Made It colony. It not only turned the tide of the First Man-Kzin War, but also brought about the rapid expansion of Human space afterwards.