unity adding component to another gameobject

//to add a new ridgidbody
gameobject.AddComponent<Rigidbody>();
//to add a new meshCollider
gameobject.AddComponent<MeshCollider>();
//Original answer by MakerBenjammin6, cleanup by me.

//referencing a gameobject
public GameObject exampleObject;
//===============================================================>
private Rigidbody rb; //example of a component

public void Awake() {
	// adding a Rigidbody component to exampleObject
	rb = exampleObject.AddComponent<Rigidbody>();
  
	// referencing an existing Rigidbody component in exampleObject
	rb = exampleObject.GetComponent<Rigidbody>();
}