Spatial indexing is a technique used in databases to efficiently manage and query spatial data, such as geographic locations or shapes. It organizes data in a way that allows for quick access and retrieval, making it easier to perform operations like searching for nearby points or finding intersections between shapes. Common methods of spatial indexing include R-trees and Quad-trees, which divide space into hierarchical structures. These structures help reduce the number of comparisons needed when searching for spatial relationships, significantly improving performance in applications like geographic information systems (GIS) and computer-aided design (CAD).