What is the difference between GameObject.GetComponent and Component.GetComponent?

First of all understand the relationship between GameObject and Component.

A GameObject is a container; you add pieces to the GameObject container to make it into a character, a light, a tree, a sound, or whatever else you would like it to be. Each piece you add is called a component.

Depending on what kind of object you want to create, you add different combinations of components to a GameObject. You can think of a GameObject as an empty cooking pot, and components as different ingredients that make up your recipe of gameplay. Unity has lots of different built-in component types, and you can also make your own components.

• GameObjects are all the same type.

• Components come in many types.

• GameObjects contain (instances of) components.

• Every GameObject contains a Transform component.

• Every component can access its gameObject.

• Every component also get convenience accessors (properties) that retrieve the corresponding properties of its gameObject, including .transform, as you have observed.

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Both the GameObject class and the Component class have a number of properties that are "shortcuts" to (other) components.

     myGameObject.transform is a shortcut for myGameObject.GetComponent<Transform>().
     myComponent.transform is a shortcut for myComponent.gameObject.GetComponent<Transform>()

the GetComponent function exists on the Component class as well. At the End both are same!!