The Nikon D5 supports a maximum video resolution of 1920 x 1080 pixels. That's over two times the video resolution of the most frequently found video resolution of 1280 x 720 pixels. A video resolution of 1920 x 1080 pixels is equivalent to Full HD video. You will require a Full HD TV or better to appreciate this level of detail.
A 1920 x 1080 pixels video resolution is in fact the best supported video resolution amongst all SLR digital cameras that have been around for a comparable time to the D5.
The worst supported video resolution amongst comparable types of camera is 640 x 480 pixels.