Question Explaining how this single file allows game to determine what is clicked from variety of objects

Hi again!

As I'm sure you know, I'm working on a scissors-paper-rock game. I've been given a version with working code created by someone else to help me, but I don't want to copy their code without understanding it decently first. I previously had created 3 different files with different classes to determine whether or not the player clicked on scissors, paper or rock.

They have given me a single file that apparently handles all of this:

Code (CSharp):

1. using ScissorsPaperRock;
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityEngine.EventSystems;
6.  
7. public class SelectObject : MonoBehaviour, IPointerClickHandler
8. {
9.     public UNIT Choice;
10.     // Start is called before the first frame update
11.     public void OnPointerClick(PointerEventData pointerEventData)
12.     {
13.         GameObject.Find("GameManager").GetComponent<GameHandler>().ProcessPlayerChoice(Choice);
14.     }
15. }
16.  

It is attached to all 3 objects. There's an event system. When I look at the attached script it has a drop down menu that allows me to select from one of the 3 enums. It seems all good.

But what I don't understand is quite how it works. Hence why I'm asking for a relatively simple (if possible) explanation. I don't want to copy their code unless I've made an effort to understand what it does. So could you please explain to me how the code works? I figure it finds what object I clicked on and determines the selection based on that, but I don't quite understand how.

Thanks!