Question about Mesh Generation

Based on this tutorial: MESH GENERATION in Unity - Basics - YouTube

So to generate a quad I would first add the vetices and then the triangles.

void CreateShape()
    {
        vertices = new Vector3[]
        {
            new Vector3(0,0,0),
            new Vector3(0,0,1),
            new Vector3(1,0,0),
            new Vector3(1,0,1)
        };

        triangles = new int[]
        {
            0, 1, 2,
            1,3,2
        };


    }

Now the question, the first triangle is between vertice 0, 1 and 2 and the second between 1, 3 and 2 but how do i know which number which vertice is? Are they numbered by the sequence I added them?

Whole code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;


[RequireComponent(typeof(MeshFilter))]
public class MeshGenerator : MonoBehaviour
{

    Mesh mesh;

    Vector3[] vertices;
    int[] triangles;

    
    void Start()
    {
        mesh = new Mesh();
        GetComponent<MeshFilter>().mesh = mesh;

        CreateShape();
        UpdateMesh();
    }

    
    void CreateShape()
    {
        vertices = new Vector3[]
        {
            new Vector3(0,0,0),
            new Vector3(0,0,1),
            new Vector3(1,0,0),
            new Vector3(1,0,1)
        };

        triangles = new int[]
        {
            0, 1, 2,
            1,3,2
        };


    }


    void UpdateMesh()
    {
        mesh.Clear();

        mesh.vertices = vertices;
        mesh.triangles = triangles;

        mesh.RecalculateNormals();
    }

}

Look’s all good but have you got a mesh renderer on the object this script is attached to?

EDIT - sorry, forgot your original question. Yes, it’s the order you add to the array.

Your vertices are inside an Array, so Vertices[0] = new Vector3(0,0,0) Vertices[1] = new Vector3(0,0,1)