Static Batching is a technical term that is extremely important in game graphics rendering and optimization (technical art). An optimization technique that pre-combines the meshes of static objects (buildings, terrain, etc.) that do not move during game execution, significantly reducing the CPU load of draw calls.
Real-world analogy: Optimizing logistics by ``combining packages destined for the same destination into one giant cardboard box and shipping them all at once,'' instead of distributing mail to each house
Static batching is a system in which multiple parcels destined for the same delivery destination (same material) that do not move are packed in advance into one giant cardboard box (combined mesh) in a warehouse and delivered all at once using one truck (one draw call).'' Because we know that the objects are absolutely static, this pre-packing combination is possible, and the time required for the CPU to write delivery instructions hundreds of times (CPU bottleneck) is dramatically reduced to zero.
Figure: Infographic that clearly illustrates the basic process flow and mechanism of Static Batching in Japanese notation
Detailed mechanism and operating principle
Build with "Static (specifically Batching Static)" checked for objects in the inspector so Unity can pre-combine them into one giant unified mesh and draw them in one go.