Enum in C# is also known as enumeration. It is used to store a set of named constants such as season, days, month, size etc. The enum constants are also known as enumerators. Enum in C# can be declared within or outside class and structs.
Enum constants has default values which starts from 0 and incremented to one by one. But we can change the default value.
Let's see a simple example of C# enum.
using System;
public class EnumExample
{
    public enum Season { WINTER, SPRING, SUMMER, FALL }  
    public static void Main()
    {
        int x = (int)Season.WINTER;
        int y = (int)Season.SUMMER;
        Console.WriteLine("WINTER = {0}", x);
        Console.WriteLine("SUMMER = {0}", y);
    }
}C# enum example changing start index
using System;
public class EnumExample
{
    public enum Season { WINTER=10, SPRING, SUMMER, FALL }  
    public static void Main()
    {
        int x = (int)Season.WINTER;
        int y = (int)Season.SUMMER;
        Console.WriteLine("WINTER = {0}", x);
        Console.WriteLine("SUMMER = {0}", y);
    }
}C# enum example for Days
using System;
public class EnumExample
{
    public enum Days { Sun, Mon, Tue, Wed, Thu, Fri, Sat };
    public static void Main()
    {
        int x = (int)Days.Sun;
        int y = (int)Days.Mon;
        int z = (int)Days.Sat;
        Console.WriteLine("Sun = {0}", x);
        Console.WriteLine("Mon = {0}", y);
        Console.WriteLine("Sat = {0}", z);
    }
}C# enum example: traversing all values using getNames()
using System;
public class EnumExample
{
    public enum Days { Sun, Mon, Tue, Wed, Thu, Fri, Sat };
    public static void Main()
    {
        foreach (string s in Enum.GetNames(typeof(Days)))
        {
            Console.WriteLine(s);
        }
    }
}C# enum example: traversing all values using getValues()
using System;
public class EnumExample
{
    public enum Days { Sun, Mon, Tue, Wed, Thu, Fri, Sat };
    public static void Main()
    {
        foreach (Days d in Enum.GetValues(typeof(Days)))
        {
            Console.WriteLine(d);
        }
    }
}