c# beginner question

[Lightning03]

What do you call those statements highlighted in red?

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
                    int choice;
                    
                    Console.WriteLine("Please select below");
                    Console.WriteLine();
                    Console.WriteLine("1. Area of a Circle");
                    Console.WriteLine("2. Area of a Rectangle");
                    Console.WriteLine("3. Area of a Cylinder");
                    Console.WriteLine();
                    choice = Convert.ToInt32(Console.ReadLine());

                    if (choice == 1)
                    {
                        Console.Clear();
                        aCircle();

                    }
                    if (choice == 2)
                    {
                        Console.Clear();
                        aRectangle();
                    }
                    if (choice == 3)
                    {
                        Console.Clear();
                        aCylinder();
                    }
                    Console.Write("Do you wish to try again? : ");
                    Console.ReadLine();
            
        }
    
        static void aCircle()
        {
            int r;
            double A;
            Console.WriteLine("Enter the radius:");
            r = Convert.ToInt32(Console.ReadLine());
            A = 3.14 * r * r;
            Console.WriteLine("The Area of circle of given radius is="+A);
            Console.ReadLine();
        }
        static void aRectangle()
        {
            int w, h;
            int ar;
            Console.WriteLine("Enter the width:");
            w = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("Enter the height:");
            h = Convert.ToInt32(Console.ReadLine());
            ar = w * h;
            Console.WriteLine("The Area of rectangle is=" + ar);
            
        }
        static void aCylinder()
        {
            double rc;
            double hc;
            double ac;
            double pi=3.14;
            Console.WriteLine("Enter the radius");
            rc = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("Enter the height:");
            hc = Convert.ToInt32(Console.ReadLine());
            ac = 2 * pi * rc*rc + 2 * pi * rc * hc;
            Console.WriteLine("The Area of cylinder is=" + ac);
            Console.ReadLine();
        }
           

            


        
    }
}

Another question.

This is an example of a constructor method:

public double multiply(double nFirst, double nSecond)
{
}

now what makes it a constructor method and how is it different from a normal method?

[Momerath]

First Question: Those are static methods. Also known as class methods.

Second Question: That's not a constructor. Constructors don't have a explicit return type, while this one does (double).

[Lightning03]

First Question: Those are static methods. Also known as class methods.

Second Question: That's not a constructor. Constructors don't have a explicit return type, while this one does (double).

oh yeah thanks, if that wasn't a constructor then what do you call it?

Also this is what I meant by constructor:

public mySampleClass()

[Momerath]

oh yeah thanks, if that wasn't a constructor then what do you call it?

It's a method.Also this is what I meant by constructor:

public mySampleClass()

A constructor has the same name as the class it is in and has no explicit return type. For example

MyClass { 
    public int Value { get; set; } // Automatic property

    public MyClass() { // Parameterless constructor

    public MyClass(int v) {  // Constructor that takes an int
        Value = v;
    }

    public MyClass(String s) { // Constructor that takes a string
        int v;
        if (Int32.TryParse(s, out v) == false) {
            throw new ArgumentException("Parameter must be an integer");
        }
        Value = v;
    }
}