Objects or GameObjects are what make up nearly everything in Unity. The characters, camera, 3D text, and lights are all a very basic-level GameObjects. Everything you see in a Unity-developed project is either GameObjects, or connected to them.
It should be pointed out that some things that you cannot see are GameObjects as well. A common practice is to create empty GameObjects so that we can apply scripts or other components to it. These objects are created to perform a function, such as to keep game scores or to handle network traffic. The one common element that all GameObjects share is the Transform component: