By default, Unity Scenes start with a ground plane, horizon line, sky, and Sun. However, these are not individual GameObjects. Instead, it is a panoramic texture mapped to the inside of a cube and we call it a skybox. The skybox is drawn in the background behind all other objects and rotates to match the current camera's orientation. When done correctly, the skybox creates an immersive environment within the scene.
Skyboxes are materials created from combining six photographs, each at 90° from each other or by capturing a single 360° equirectangular panoramic image. The six-photo method, known as a Cubemap, can be created by shooting images from a single position in each direction; up, right, left, front, back, and down. Equirectangular images are created by capturing or stitching together images into a 3D projection:
