Unity 101 - PlayerController.cs

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

public class PlayerController : MonoBehaviour
{
    // The speed at which the player will move when going left and right
    public float speed;

    // The amount of force that the player will jump with
    public float jumpForce;

    // A reference to a Rigidbody2D component that's on our character
    Rigidbody2D rb;

    // Start is called before the first frame update
    void Start()
    {
        // Get the Rigidbody2D that's on our character
        rb = GetComponent<Rigidbody2D>();
    }

    // Update is called once per frame
    void Update()
    {
        // If the player is pressing the A key
        if(Input.GetKey(KeyCode.A))
        {
            // Time.deltaTime is the time between this frame and the last frame
            // We use this whenever moving because we want to keep the speed constant
            // Even if our frame rate drops
            Vector2 delta = new Vector2(-speed * Time.deltaTime, 0);

            // The transform.Translate function moves our GameObject directly by a certain amount
            transform.Translate(delta);
        }
        // If the player is pressing the D key
        else if (Input.GetKey(KeyCode.D))
        {
            // Same thing as above, except we don't negate the speed
            Vector2 delta = new Vector3(speed * Time.deltaTime, 0);
            transform.Translate(delta);
        }

        // Input.GetKeyDown checks for weather the space key was pressed this frame
        if(Input.GetKeyDown(KeyCode.Space))
        {
            Vector2 forceToAdd = new Vector2(0, jumpForce);

            // AddForce adds an actual force to the object
            rb.AddForce(forceToAdd);
        }
    }
}