Page tabs are the labels that appear along the right edge of the page. They belong inside of sections. As you switch from section to section, you'll see all the page tabs pertaining to that section change to display the ones associated with the current section. This is where your notes and other content lives.
You can add a new page by clicking the New Page button that appears above the page tabs. If you prefer to use the keyboard, you can press <Ctrl + N> to create a new page.
Subpages, (also known as grouped pages), are the page tabs that appear slightly indented, such as "Passwords" in this picture. This provides a way to further organize your pages.
The slight indentation indicates that they belong to a group of pages with the main page as its 'parent page'.
You can put any notes or content onto a subpage just like you can on a main page. To create a new subpage beneath the current one, simply click the small arrow next to the New Page button -> and select New Subpage. You can also right-click any page and select New Subpage to create a new one immediately beneath it. Or for you keyboard lovers out there, you can press <Ctrl + Shift + N>.
One of the most compelling things about a page in OneNote is the versatility in which it can store your stuff. You can put just about every kind of content you can imagine on the page surface. It can handle, text, ink, drawings, pictures, audio, video, tables, documents and files of every kind. What's more, you don't have to do anything special for OneNote to handle any of these things. It just knows how to deal with them.
Content added to a page appears inside a container, known as an outline. The outline contains a handle along the top to show that you can grab it and move it around.
Each note inside the outline is known as an element. Each element has a small grab handle that appears to the side to show that it can be repositioned inside the outline. You can also use the grab handle to drag content outside the outline if you desire.
The outline border and the element grab handle only appear if your mouse is hovering over them. To some people this is a nuisance, because these things are constantly flashing as your mouse moves across the page. If you want to reduce the amount the visual 'noise' on the page, you can hide the outline borders. To do this, click Tools -> Options -> Display -> remove the checkmark from 'Show note containers on pages'.