NotebookCreate

NotebookCreate[ ] creates a new open notebook in the front end.

NotebookCreate[options] sets up the specified options for the new notebook.

NotebookCreate will by default create a notebook with name "Untitled-n".

Unless you set the option Visible->False, NotebookCreate will cause a new window to appear on your screen.

See The Mathematica Book: Section 2.10.3.

See also: NotebookOpen, NotebookClose.