TANK! Tutorial-GetComponent

Hi. I’m new in Unity. I’m actually a electrical engineer. So A week ago. I started learning Tank tutorial.
In ShellExplosion script, there is a code:

Rigidbody targetRigidbody = colliders*.GetComponent ()*

OK, as far as I know, The game object contain component. So when using GetComponent that mean you get a component from a gameobject and assign it to a instance.
But the code above, collider is a component. How can it contain another component?
The instructor said the code will scan all colliders and if they have rigidbody inside then assign the Rigidbody for “targetRigidbody”?
The next code is even more confused:
TankHealth targetHealth = targetRigidbody.GetComponent ();
The TankHealth is script is written before, so using it to call function TakeDamage().
But again, targetRigidbody is Rigidbody, why does it have script?
Can you help me? Thank

It just retrieves a component on the same game object as the collider/rigidbody/other component.