Visual Studio Code – My visual studio script is not working in Unity

I just started game development and got into a problem
whenever I load my Visual Studio code into Unity it says
The refrenced script unknown on this behaviour is missing

This is my script

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

public class VirtualManMovement : MonoBehaviour
{
    // Start is called before the first frame update
    void Start()
    {
        Debug.Log("Hello, World!") ;
    }

    // Update is called once per frame
    void Update()
    {
        
    }
}

I need a solution for this