What do we mean by Live Gamer Extreme 2 uncompressed raw data support?

To confirm what uncompressed format support means:

The AVerMedia Live Gamer Extreme 2 (GC551) delivers ultra low latency uncompressed 1080p 60fps video over USB 3.1 (Gen 1) Type-C  connection for HDMI sources.

The main feature that the LGX 2 touts is ultra-low latency uncompressed video, meaning you see the game as intended with no real lag or delay between what you'd see on your TV.

Without hardware encoding process, Live Gamer Extreme 2 can capture uncompressed raw data and stream it with minimal latency.

Please note that the recorded file as confirmed on official product page

will be at MP4 format.