This page kind of explains it:
http://ergo.human.cornell.edu/ahtutorials/typingposture.html
The middle image is how I used to be. My fixed desk was too high (even with my chair at maximum height) and so my arm/wrist was bent up.
I then got a height-adjustable desk and a monitor stand, and I made my setup more like the top image. However, my monitor is quite a bit higher that what is shown in that first image. I look straight ahead and don't tilt my head down.