help me under stand the key word "new" in c#

hey guys

I can't understand how to use the "new" key word in c#

please explain me in detail that, thank you

If I just said something wrong, forgive me, my English is very bad

for example

int[] numbers = new int[];

or


using System.IO
StreamReader myreader = new StreamReader("Values.txt");

or

etc
class Program
{
static void Main(string[] args)
   {
      car mynewcar = new car();
   }
}
class car
{
public string etc
public int etc
}

ps: explain me just about the word "new", how and when we use it, I have been crazy about that word :)

thanks