An octree is a tree data structure used to partition three-dimensional space. It divides the space into eight smaller regions, or "octants," allowing for efficient organization and retrieval of spatial data. This structure is particularly useful in computer graphics, gaming, and geographic information systems, where managing large amounts of 3D data is essential. Each node in an octree represents a cubic volume of space, and as objects are added, the tree subdivides further to maintain a balanced structure. This hierarchical organization helps optimize tasks like collision detection, rendering, and spatial queries, making it easier to manage complex 3D environments.