Not really understanding Backing Fields with custom get; and set;

  internal class Person
  {
    private string _name;
    public string Name { get { return _name; } }

    private int _age;
    public int Age
    {
      get { return _age; }
      set
      {
        if (value >= 0)
          _age = value;
        else
          Console.WriteLine("Age cannot be below 0!");        
      }
    }

    public Person(string name, int age)
    {
      _name = name;
      Age = age;
    }

    public void GreetPerson()
    {
      Console.WriteLine($"Welcome, {_name}! You're {_age} years old!");
    }
  }