Hi I have recently started GR and have found the mathematics to be quite easy (have encountered differential manifolds and tensor calculus in other subjects), but the physics is troubling me, allow me to elaborate. In special relativity, we have a very intuitive idea of how observations work, there are global inertial frames as in classical mechanics, and to link one inertial observer to another, we simply use the Lorentz transform. I find this very intuitive, even though the concepts of absolute time and distance have been abandoned, the invariant interval makes up for that. However, I have no idea how things are suppose to work in GR. I understand that the equality between inertial mass and gravitational mass rules out any possibility for a global inertial frame, but that's where my intuition drops dead. How are observers treated in GR?