Creating a text file

Hello

Have a look please at the code below:

class Test
{
    public static void Main()
    {
        using (StreamWriter sw = new StreamWriter("TestFile.txt"))
        {
            // Add some text to the file.
            sw.Write("This is the ");
            sw.WriteLine("header for the file.");
            sw.WriteLine("-------------------");
            // Arbitrary objects can also be written to the file.
            sw.Write("The date is: ");
            sw.WriteLine(DateTime.Now);
        }
    }
}

1.what is that using keyword for? what does it do? i thought using is just for namespaces.
2.where is this file created? in C:\ ?
3.what does he mean in the "Arbitrary objects..." comment?