Check out example codes for "scene manager unity". It will help you in understanding the concepts better.

Code Example 1

using UnityEngine;
using UnityEngine.SceneManagement;

public class ExampleScript: MonoBehaviour
{
     public string Scene; // Put int the Name of the scene you want to load :)
     // Active when the game/app starts :)
    void Start()
    {          
    SceneManager.LoadScene(Scene);

    }
}

Code Example 2

using UnityEngine.SceneManagement;

int buildIndex = 0;
//Load the scene with a build index
SceneManager.LoadScene(buildIndex);

Code Example 3

using UnityEngine;
using UnityEngine.GameManagement;

public class NextLevelLoader : MonoBehaviour

public void LoadScene () 
{

	SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);

}

Code Example 4

SceneManager.LoadScene(scenename);

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