This is a simple 3D cube primitive with six faces. The position, size, rotation, texture and collision of the cube can be customized. You can use cube primitives to build walls, buildings, etc…
It is a best practice to use as fewer cubes as possible when building your map. For example, you can use one cube with bricks texture instead of many cubes with brick textures.
You can also use invisible cubes as collision objects for complex scenes.