GameObjects have some components that make them behave in a certain way. For instance, select Main Camera and look at the Inspector panel. One of the components is the camera. Without that component, it will cease being a camera. It would still be a GameObject in your scene, just no longer a functioning camera.
When we refer to components, we are basically referring to the available functions of a GameObject, for example, the human body has many functions, such as talking, moving, and observing. Now let's say that we want the human body to move faster. What is the function linked to that action? Movement. So in order to make our body move faster, we would need to create a script that had access to the movement component and then we would use that to make the body move faster. Just like in real life, different GameObjects can also have different components, for example, the camera component can only...