Hybrid (discrete/continuous) systems are systems that exhibit both discrete state and continuous state dynamics. In addition, these two aspects of system behavior interact to such a significant extent that they cannot be decoupled and must be analyzed simultaneously. We consider the modeling, simulation and sensitivity analysis of hybrid systems, with particular emphasis on the interactions between discrete and continuous subsystems. The discussion focuses on the hybrid automation representation of continuous time hybrid systems. Topics discussed include state event location, transfer functions for the continuous state at discontinuities, and parametric sensitivity analysis of hybrid systems.