Check out example codes for "how to make movement in unity in c#". It will help you in understanding the concepts better.

Code Example 1

public Rigibody rb;
public float _write_your_speed_x;
public float _write_your_speed_in_y;
public float write_your_speed_in_z;

void Update(){
  if(input.GetKey(keycode.Uparrow)
  	trasform.position += new vector3(_write_your_speed_in_x,_write_your_speed_in_y,write_your_speed_in_z);
  else 
     transform.position += new vector.zero;
}

Code Example 2

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

public class PlayerMovement : MonoBehaviour
{
    private string moveInputAxis = "Vertical";
    

    public float moveSpeed = 0.1f;
    public Rigidbody rb;
    public bool cubeIsOnTheGround = true;


    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody>();
    }
    
    // Update is called once per frame
    void Update()
    {
       float moveAxis = Input.GetAxis(moveInputAxis); 

       ApplyInput(moveAxis);

       if(Input.GetButtonDown("Jump") && cubeIsOnTheGround == true)
       {
           rb.AddForce(new Vector3(0, 7, 0), ForceMode.Impulse);
           cubeIsOnTheGround = false;
       } 

    private void ApplyInput(float moveInput)
    {
        Move(moveInput);
    }

    private void Move(float input)
    {
        transform.Translate(Vector3.forward * input * moveSpeed);
    }    

    private void OnCollisionEnter(Collision collision) {
        if(collision.gameObject.tag == "Ground") {
            cubeIsOnTheGround = true;
        }
    }
}

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