How to use the nameof keyword in C#

using System;
class MainClass
{
    static void Main()
    {   
        // Declaration of the variable     
        string accountName = "Foo";
        // Prints the name of the variable, courtesy of the 'nameof' keyword
        Console.WriteLine("The name of the variable is: " + nameof(accountName));
        // Prints the value of the variable
        Console.WriteLine("The value of the variable is: " + accountName);
    }
}

using System;
class MainClass
{
    static void Main()
    {   
        // Declaration of the variable     
        int catsAge = 30;        
        // Validates the age
        ValidateAge(catsAge);
        // Prints the result of the execution to the user
        Console.WriteLine("Method ran successfully!");
    }
    static void ValidateAge(int catsAge)
    {
        // Verifies is under the minimum value
        if(catsAge < 0)
        {
            // Throws an exception with a message and the name of the invalid parameter
            throw new ArgumentOutOfRangeException(nameof(catsAge), "Invalid age.");
        }               
        // Verifies exceeds the maximum value
        if(catsAge > 25)
        {
            // Throws an exception with a message and the name of the invalid parameter
            throw new ArgumentOutOfRangeException(nameof(catsAge), "Cats don't live that long, unfortunately.");
        }            
    }
}

class WildWestCity : INotifyPropertyChanged
{
    // Declares the event
    public event PropertyChangedEventHandler? PropertyChanged;
    // Declares the variable
    private string name;
    public string Name
    {
        get { return name; }
        set
        {
            // Stores the value in the variable
            name = value;
            // Calls the method that invokes the event, supplying its name as the parameter
            OnPropertyChanged(nameof(Name));
        }
    }
    // Declares the variable
    private int population;
    
    public int Population
    {
        get { return population; }
        set
        {
            // Stores the value in the variable
            population = value;
            // Calls the method that invokes the event, supplying its name as the parameter
            OnPropertyChanged(nameof(Population));
        }
    }
    public void OnPropertyChanged(string property)
    {
        // Invokes the event
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
    }
}