Unity NullReferenceException: Object reference not set to an instance of an object how to overcome?

Question

Unity

Good day, I decided to start working with Unity over the weekend. Knowledge of C# is relatively low. To begin with, I decided to make a 2D platformer, it seems that this is the easiest.

the code

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

public class player_controls : MonoBehaviour
{
    Rigidbody2D rb;
    Animator anim;
    public float speed = 6f;
    void Start()
    {
        rb = GetComponent<Rigidbody2D>();
    }

    // Update is called once per frame
    void Update()
    {
        if (Input.GetKeyDown(KeyCode.UpArrow))
        {
            jump();
        }

        if (Input.GetAxis("Horizontal") == 0)
        {
            anim.SetInteger("animation", 1);
        } 
        else
        {
            FlipHero();
            anim.SetInteger("animation", 2);
        }
    }

    
    void FlipHero()
    {
        if (Input.GetAxis("Horizontal") < 0)
        {
            transform.localRotation = Quaternion.Euler(0, 180, 0);
        } else
        {
            transform.localRotation = Quaternion.Euler(0, 0, 0);
        }
    }

    void FixedUpdate()
    {
        rb.velocity = new Vector2(Input.GetAxis("Horizontal") * speed, rb.velocity.y);
    }
    void jump()
    {   
        rb.AddForce(transform.up * 12f, ForceMode2D.Impulse);
    }
}

And the error itself: NullReferenceException: Object reference not set to an instance of an object
player_controls.Update () (at Assets/scripts/player_controls.cs:25)

Google, Google and similar questions looked, did not help much.

It's just that the animation does not work ... How to be, please describe in an accessible language.)

Answer 1

Not so Googled and not looked there. Your anim is not assigned.

Answer 2

C# knowledge is relatively low

OK, in an accessible language - learn seasharp first. The error has little to do with the unit.