The GameObject is the most important concept in Unity. Every object in a game is a GameObject. Scenes are then, at their simplest, lists of GameObjects.
GameObjects are the Characters, items, background objects, obstacles, platforms, menus, trees, sources of audio, buttons, lights, cameras, and so on.
On it’s own, a GameObject is … nothing? A name, a position in space. It doesn’t do anything. To make it do things, we give GameObjects components. Think of these as properties, or behaviors.
As you can read in Unity Manual:
“GameObjects are the fundamental objects in Unity that represent characters, props and scenery. They do not accomplish much in themselves but they act as containers for Components, which implement the real functionality.”Unity Manul: Creating Gameplay>GameObjects>GameObject
We can’t get very far with just GameObjects. We need to add Components, the most important of which may be the Transform component.