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 retrieval based on spatial relationships, making it easier to perform operations like finding nearby points or determining overlaps between shapes. Common spatial indexing structures include R-trees and Quad-trees, which divide space into manageable sections. These structures help reduce the amount of data that needs to be searched, improving performance for applications like geographic information systems (GIS) and location-based services.