What are enums in C?

#include<stdio.h>

enum color {
  red,
  green,
  blue
};

int main() 
{
  // Initializing a variable that will hold the enums
  enum color current_color = red;
	printf("Value of red = %d \n", current_color);	

	current_color = green;
	printf("Value of green = %d \n", current_color);	

	current_color = blue;
	printf("Value of blue = %d \n", current_color);	
	return 0;
}

#include<stdio.h>

enum suit {
    club = 0,
    diamonds = 10,
    hearts = 20,
    spades = 30
};

int main() 
{
    // Initializing a variable that will hold the enums
    enum suit current_card = club;
	printf("Value of club = %d \n", current_card);	

	current_card = hearts;
	printf("Value of hearts = %d \n", current_card);	
	return 0;
}

#include <stdio.h> 
enum day {sunday , monday, tuesday, 
          wednesday, thursday, friday, saturday}; 
  
int main() 
{
  // Enums can also take their integer equivalent values
  enum day today = 4;

  switch(today)
  {
    case sunday:
      printf("The day today is Sunday");
      break;
    case monday:
      printf("The day today is Monday");
      break;
    case tuesday:
      printf("The day today is Tuesday");
      break;
    case wednesday:
      printf("The day today is Wednesday");
      break;
    case thursday:
      printf("The day today is Thursday");
      break;
    case friday:
      printf("The day today is Friday");
      break;
    default:
      printf("The day today is Saturday");
  }
    return 0; 
}