Vector Prime was a Yuuzhan Vong term for entry point in the Outer Rim Territories and where their invasion of the galaxy began. The extra-galactic invasion needed to start in Vector Prime due to it being the only place known where the forces could penetrate a circumferential hyperspace barrier surrounding the galaxy. It was close to outer edges of the Dalonbian sector, near the Helska system.
However, other Yuuzhan Vong suggested it had been chosen due to its proximity to the New Republic and Imperial Remnant border, which made both parties less able to respond.