Na'vi is the species of natives that live on the world "Pandora". Their skin is blue and their height is 3.1 metres tall, ergo very tall compared to Earthlings (10 feet meaning 3.05 meters).
The resource-chasing Earthlings made hybrid-beings that were similar to Na'vi.
Note: One such blue hybrid was piloted by Jake, who went to study the native culture. The R.D.A. (Resources Development Administration) sent him to convince them to move away from the places that have the minerals that the humans wanted. This would avoid fighting when the Earthlings would go there to dig up the precious unobtainable "unobtanium".