Login Pages

I am new to WordPress. I know there is a way to add a login to a website, but is there a way to add a login to a specific page on a website? If I do this, can I add more pages once the person is logged in?

I want my users to be able to see 4 of my pages, but the 5th page I only want specific users to be able to see.

Does anyone know how to do this? Is there a plug-in?

Thanks!