Social mobility refers to changes in social position or status within a society. There are two types of social systems - open systems that emphasize competition and allow social mobility based on individual success, and closed systems that limit social mobility. The passage discusses different types of social mobility, including horizontal, vertical, intergenerational, and intragenerational mobility. It also examines factors that influence occupational mobility in the US, such as education, race/ethnicity, and gender. While education once guaranteed jobs, degrees are now more common. Mobility is also more limited for African Americans and Hispanics compared to other groups. Women also face more restrictions in career opportunities than men.