Dumb this down for me?

I know a little programming with c# I found this in a youtube video and i learn better when things are dumbed down for me. I dont know what a Quaternium is (Idk how to spell, matf.abs, euluer angles and a float.help me please?

using UnityEngine; using System.Collections;

[RequireComponent(typeof(CharacterController))]

public class PlayerController : MonoBehaviour {

 // Handling
 public float rotationSpeed = 450;
 public float walkSpeed = 5;
 public float runSpeed = 8;

 //System

 private Quaternion targetRotation;

 // Components

 private CharacterController controller;


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

 void Update () {
     Vector3 input = new Vector3(Input.GetAxisRaw ("Horizontal"),0, Input.GetAxisRaw ("Vertical"));
     if (input != Vector3.zero) {
     targetRotation = Quaternion.LookRotation (input);
         transform.eulerAngles = Vector3.up * Mathf.MoveTowardsAngle(transform.eulerAngles.y,targetRotation.eulerAngles.y,rotationSpeed * Time.deltaTime);

 
 }
     Vector3 motion = input;
     motion *= (Mathf.Abs (input.x) == 1 && Mathf.Abs (input.z) == 1)?.7f:1;
     motion *= (Input.GetButton("Run"))?runSpeed:walkSpeed;
     motion += Vector3.up * -8;

     controller.Move(motion * Time.deltaTime);

} }