I've heard about VRF's and GRF's, but was is the difference between those 2? (cisco)
GRF is the global routing and forwarding table. Also known as the default VRF in other vendors. It's simply the regular RIB used when no VRFs are used, or the original VRF when other VRFs are used.
A VRF is a virtual routing and forwarding table which allows a physical router to run a 'virutal' router with it's own RIB and FIB and routing protocols.