Monte Carlo Event Generators

Monte Carlo event generators are essential components of almost all experimental analyses and are also widely used by theorists and experiments to make predictions and preparations for future experiments. They are all too often used as "black boxes", without sufficient consideration of their component models or their reliability. In this set of three lectures we hope to open the box and explain the physical bases behind the models they use. We focus primarily on the general features of parton showers, hadronization and underlying event generation.