A 6-inch screen below the main 15-incher is for watching a stream, chatting, listening to music or monitoring your system stats via the command center. To Windows it looks just like a second monitor, which means you can drag any window down to it and display any type of content.
On the right you'll find a USB-C/Thunderbolt connector and a third USB-A. Because the laptop lacks a DisplayPort connection, it doesn't support G-Sync on an external monitor. (G-Sync requires a connection on the GPU bus, and USB-C/Thunderbolt connections are always to the integrated GPU.)