You have entered "charactercontroller" instead of "CharacterController" in the Script.
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class PlayerController : MonoBehaviour
{
CharacterController characterController;
public float MovementSpeed = 1;
public float Gravity = 9.8f;
private float velocity = 0;
private void Start()
{
characterController = GetComponent<CharacterController>();
}
void Update()
{
// player movement - forward, backward, left, right
float horizontal = Input.GetAxis("Horizontal") * MovementSpeed;
float vertical = Input.GetAxis("Vertical") * MovementSpeed;
characterController.Move((transform.right * horizontal +
transform.forward * vertical) * Time.deltaTime);
// Gravity
if (characterController.isGrounded)
{
velocity = 0;
}
else
{
velocity -= Gravity * Time.deltaTime;
characterController.Move(new Vector3(0, velocity, 0));
}
}
}
Please correct your script.