Spain's use of caste systems refers to the hierarchical social structure established during the colonial period in Spanish America, which categorized individuals based on their race, ethnicity, and ancestry. This system created a complex social order where Spaniards, mixed-race individuals, Indigenous peoples, and Africans were ranked differently, affecting their rights, privileges, and roles within society. The caste system played a crucial role in organizing labor, shaping social interactions, and maintaining power dynamics in colonial societies.