This review presents the state of the art about the modeling of Inverter-Based Resources (IBR's), in the context of bulk power systems with high penetration of Variable Renewable Energy (VRE) and the impact of these resources on the dynamics. The discussion on a precise modeling through EMT or RMS models this new dynamic - be it detailed or reduced - is still open, a consequence of large-magnitude phenomena whose real systemic response has not been able to be satisfactorily represented.