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

Code Example 1

//Simple 2D:
   private Rigidbody2D RB;
    public float speed = 50f;
   
   
    void Start()
    {      
        RB = GetComponent<Rigidbody2D>();        
    }

    void Update()
    {
        if (Input.GetKey(KeyCode.D))
        {
            RB.AddForce(Vector3.right * speed * Time.deltaTime);
        }
        if (Input.GetKey(KeyCode.A))
        {
            RB.AddForce(Vector3.left * speed * Time.deltaTime);
        }
        if (Input.GetKey(KeyCode.W))
        {
            RB.AddForce(Vector3.up * speed * Time.deltaTime);
        }
        if (Input.GetKey(KeyCode.S))
        {
            RB.AddForce(Vector3.down * speed * Time.deltaTime);
        }       
    }

Code Example 2

using UnityEngine;
using System.Collections;

// This script moves the character controller forward
// and sideways based on the arrow keys.
// It also jumps when pressing space.
// Make sure to attach a character controller to the same game object.
// It is recommended that you make only one call to Move or SimpleMove per frame.

public class ExampleClass : MonoBehaviour
{
    CharacterController characterController;

    public float speed = 6.0f;
    public float jumpSpeed = 8.0f;
    public float gravity = 20.0f;

    private Vector3 moveDirection = Vector3.zero;

    void Start()
    {
        characterController = GetComponent<CharacterController>();
    }

    void Update()
    {
        if (characterController.isGrounded)
        {
            // We are grounded, so recalculate
            // move direction directly from axes

            moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0.0f, Input.GetAxis("Vertical"));
            moveDirection *= speed;

            if (Input.GetButton("Jump"))
            {
                moveDirection.y = jumpSpeed;
            }
        }

        // Apply gravity. Gravity is multiplied by deltaTime twice (once here, and once below
        // when the moveDirection is multiplied by deltaTime). This is because gravity should be applied
        // as an acceleration (ms^-2)
        moveDirection.y -= gravity * Time.deltaTime;

        // Move the controller
        characterController.Move(moveDirection * Time.deltaTime);
    }
}

Code Example 3

using UnityEngine;

public class PlayerMovement : MonoBehaviour
{
    [SerializeField] private float speed = 5.0f;

    private void Update()
    {
        var horizontal = Input.GetAxis("Horizontal");
        var vertical = Input.GetAxis("Vertical");
        transform.Translate(new Vector3(horizontal, 0, vertical) * (speed * Time.deltaTime));
    }
}

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