Japan's global navigation satellite system (GNSS).
Eventually, QZSS is planned to be a full, independent GNSS similar the USA's GPS. But in its initial deployment, QZSS is designed to piggyback on GPS, providing more accuracy for GPS devices operating in the Asia-Pacific region.
There are multiple GNSS in operation for Earth, including Europe's Galileo, Russia's GLONASS, China's BeiDou, and India's NavIC. They work similarly to GPS, but each is operated separately.
Phones and other devices can use multiple GNSS simultaneously to improve location accuracy and speed.