_className means in dart code example

Example 1: class in dart

class class_name {  
	//rest of the code here:
}

Example 2: dart class

// entry point
void main(){

  // using the Dog class - creating an instance of this class
  var myDog = Dog();
  
  // assigning values to the newly clreated instance
  myDog.breed = 'Poodle';
  myDog.name = 'Jack';
  myDog.color = 'Brown';
 
  // displaying the values on the console 
  print(myDog.breed);
  print(myDog.name);
  print(myDog.color);
}

// Dog class 
class Dog{

  // class properties
  String breed;
  String name;
  String color;
}