WiFi-6 is the consumer-friendly term for 802.11ax, the latest version of the 802.11 wireless networking standard. It's an upgraded standard that compatible devices can take advantage of to transmit WiFi signals more efficiently. WiFi-6 contains more information into each signal set, which means they are able to communicate with more devices faster.
WiFi-6 is designed to work better in meshed networks than previous WiFi standards. Instead of boosting speeds for individual devices, WiFi-6 is all about improving the network as a whole when multiple devices are connected.