When to instantiate an object with the new keyword

Hi there,

I have a basic question:

When should I use the new keyword to instantiate an object and when should I just declare the object using the object type , e.g:

Dim TextBox1 As New TextBox() vs. Dim TextBox1 As TextBox.

My question is more generic than this example, and I would like to know what are the different cases I should use the new keyword.

Thanks.
...