Koppen's classification of climate is based on two primary factors: precipitation and temperature. These factors are used to classify the world's climates into five major groups, which are further subdivided into smaller groups based on other factors such as seasonality, humidity, and wind patterns. The classification system takes into account the amount and distribution of rainfall throughout the year and the average temperature of the warmest and coolest months. By combining these two factors, Koppen's classification provides a comprehensive system for understanding the major climatic regions of the world.