how to insert a blank or empty page with or without numbering

How to insert a blank / empty page with numbering

To insert a blank page, you need to this:

\newpage
\thispagestyle{empty}
\mbox{}
\newpage

The idea is that there is something empty or invisible (mbox hack)

How to insert blank / empty page without numbering

It is necessary to add in preamble the afterpage package and to define a macro for example \ myemptypage which will subtract one page to the counter:

\usepackage{afterpage}
\newcommand\myemptypage{
    \null
    \thispagestyle{empty}
    \addtocounter{page}{-1}
    \newpage
    }

Then you must use this macro in your LateX document:

\myemptypage

this page will not be counted in your document.