GameObjects can be static, or dynamic (not static). Static GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary and dynamic GameObjects behave differently in Unity’s occlusion cullingA that disables rendering of objects when they are not currently seen by the camera because they are obscured (occluded) by other objects. More info
See in Glossary system:
To determine whether a dynamic GameObject acts as a occludee, you can set the Dynamic Occlusion property on any type of Renderer component. When Dynamic Occlusion is enabled, Unity culls the Renderer when a Static Occluder blocks it from a CameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
See in Glossary’s view. When Dynamic Occlusion is disabled, Unity does not cull the Renderer when a Static Occluder blocks it from a Camera’s view.
Dynamic Occlusion is enabled by default. You might want to disable Dynamic Occlusion to achieve specific effects, such as drawing an outline around a character who is behind a wall.
If you are certain that Unity should never apply occlusion culling to a particular GameObject, you can disable Dynamic Occlusion to save on runtime calculations and reduce CPU usage. The per-GameObject impact of these calculations is very small, but at sufficient scale this might benefit performance.