Post
Divide the game world into chunks so the engine only thinks about what is nearby instead of everything at once.
Spatial partitioning is the family of techniques that divide a game world into regions so the engine can quickly determine which objects are near each other without checking every object against every other object. Quadtrees split 2D space into four sections recursively, octrees do the same in 3D, BSP trees carve space with planes, and spatial hashing maps positions to grid cells. Without these structures, collision detection alone would grind a game to a halt -- checking 10,000 objects against each other is 100 million checks per frame. With spatial partitioning, you only check objects that share the same region.
Example
Minecraft uses a chunk-based spatial partitioning system where the world is divided into 16x16 block columns. Only chunks near the player are loaded and simulated, which is how an effectively infinite world can run on modest hardware.
Why it matters
Every large-scale game depends on spatial partitioning to maintain performance. It is the reason open-world games do not immediately catch fire when you look at a city full of NPCs, vehicles, and physics objects all existing simultaneously.
Related concepts