Social stratification refers to a society's hierarchical ranking and categorization of people based on factors like wealth, income, race, education, and power. Societies stratify into layers with some groups having more access to resources and higher social standing than others. While caste systems assign social standing rigidly at birth, class systems allow for some social mobility between classes based on individual achievement and attributes. Key aspects of social stratification include social classes, gender, race/ethnicity, and age/disability, which can influence life chances and access to opportunities.