The document discusses various indicators used to measure development, including economic indicators like GDP and social indicators like life expectancy. It explains that composite indicators which combine multiple factors, like the Human Development Index, provide a more comprehensive picture of a country's development level than any single indicator. Reasons for differences in development levels between countries include natural resources, industrialization, political stability, location, and access to trade. Within countries, there are also often disparities between urban and rural areas in terms of access to services.