This document provides an overview of the concept of nationalism and its evolution over time. It discusses definitions of nationalism, forms that nationalism can take, and the importance of understanding nationalism. The introduction explains that to fully comprehend nationalism today, one must understand its origins, characteristics and changing nature over history as nationalism has evolved in complex ways. The chapter aims to explain what nationalism is, different types of nationalism, and the relevance of nationalism. It seeks to enable readers to define nationalism, describe its sources and types, and understand the need for nationalism.