what is a enum in unity code example

Example 1: unity enum

using UnityEngine;
using System.Collections;

public class EnumScript : MonoBehaviour 
{
    enum Direction {North, East, South, West};

        void Start () 
    {
        Direction myDirection;
        
        myDirection = Direction.North;
    }
    
    Direction ReverseDirection (Direction dir)
    {
        if(dir == Direction.North)
            dir = Direction.South;
        else if(dir == Direction.South)
            dir = Direction.North;
        else if(dir == Direction.East)
            dir = Direction.West;
        else if(dir == Direction.West)
            dir = Direction.East;
        
        return dir;     
    }
}

Example 2: unity enum

private enum State
{
	Idle,
    Walk,
    Attack,
}