Using the search function you can search through a local set of data aswell as through the whole active SharePoint-workspace. The search function recursively searches through all subpages of the current active page. This means, that you need to switch to the root-page of the workspace if you would like to perform a search within the whole workspace. Otherwise the search will begin on the current page.
The search function is annotated with footnote (3) in the picture Terms on the Introduction page.