The Demographic Transition Model (DTM) describes population growth in four stages. In Stage 1, both birth rates and death rates are high, leading to low population growth. In Stage 2, death rates decline due to medical advancements, while birth rates remain high, causing rapid population growth. Stage 3 sees a decline in birth rates due to urbanization and education, slowing growth. In Stage 4, both birth and death rates stabilize at low levels, leading to a stable or declining population. Most developed countries are in Stage 4, while developing nations are in Stages 2 and 3.