I've been curious about this for some time now and i still don't fully get it.

Here on phoronix sometimes i see mesa and mesa 3d in combination with galium3d ... and i'm getting confused by it.

What exactly is Galium3d?
How do the state trackers work in Galium3d?
Where does mesa fit in this picture..? isn't galium3d replacing mesa/mesa 3d?
What is meas 3d or is it just mesa..?

Enough confusion as you can see.
Could someone please explain to me in clear understandable language what the new Galium3d is exactly and how state trackers and mesa fir within this?

(a diagram would be nice as well)