Destroying upon collision

Im new can someone lend a helping me understand this script.

 using UnityEngine;
 using System.Collections;
 
 public class ExampleClass : MonoBehaviour {
     public Transform explosionPrefab;
     void OnCollisionEnter(Collision collision) {
         ContactPoint contact = collision.contacts[0];
         Quaternion rot = Quaternion.FromToRotation(Vector3.up, contact.normal);
         Vector3 pos = contact.point;
         Instantiate(explosionPrefab, pos, rot) as Transform;
         Destroy(gameObject);
     }
 }