Keeping homepage content when opening a post/portfolio item on homepage

Hi Some sites seem to hang onto the homepage content even when you open a post or portfolio item (does this make it a one page site?) the homepage content just moves down the page a bit so you can scroll down to it. It means you don't have to keep clicking home to reach more content. Can this be done on Everest Pro or any of the Catch themes? Is there name for this type of set up? many thanks!