I assume you are talking about the demographic transition model. Stage 2 countries have very high birth rates and somewhat falling death rates. Stage 2 country examples are Sub-Saharan Africa countries like Zimbabwe or Angola. Stage 3 is characterized by a population explosion (a large increase in population). The death rate falls, and the birth rate falls slightly (sign of industrialization). These countries are developing countries like Mexico or Indonesia. Stage 4 is where both the birth rate and death rates are low, such as more developed countries. Stage 4 countries are like the United States or China.