This document provides an overview of musical theatre, including its history and key elements. It discusses the origins of musical theatre in operetta and how shows like Oklahoma established the integrated form where music, dialogue and dance advance the plot. The golden age of musicals from the 1940s-1960s produced famous works before genres like rock musicals and mega-musicals became popular in later decades. Current musicals tend to focus on spectacle but some unusual critically acclaimed shows have emerged.