how to mark two objects and collision to explode and play the sound

Questions & Answers
1

Hi, how do I tag the second object in the code below?
Code:
public class DestroyByContact2 : MonoBehaviour
{

public AudioClip impact;
AudioSource audioSource;
public GameObject explosion; // drag your explosion prefab here

void Start()
{
    audioSource = GetComponent<AudioSource>();
}


void OnCollisionEnter(Collision collision)
    {

    if (collision.gameObject.tag == "Asteroids" ) { 
    
        GameObject expl = Instantiate(explosion, transform.position, Quaternion.identity) as GameObject;

        audioSource.PlayOneShot(impact, 0.7F);
        Destroy(collision.gameObject); // destroy the grenade
        
        Destroy(expl, 5); // delete the explosion after 2 seconds
         }
    }

}

2

The game object with the script attached can be accessed with gameObject. The second game object can be accessed by using collision.gameObject