The "contents" tab shows what's in the current folder.  This listing should be somewhat familiar, because it looks roughly like what you might see in Windows Explorer (or the Finder, for you Mac users), so probably the most confusing aspect is determining what "the current folder" actually is, so I'll give a few examples.

• This page you're reading ("The Folder Contents Tab") lives in the "Full Tutorial" folder; the contents tab will show a list of the other Tutorial pages.  This makes sense if you look at the breadcrumbs at the top or the navigation to the left.
  
• If I'm logged in and looking at the homepage of my site, then my current folder is the top level folder that contains the whole site.
• If I were currently looking at a folder instead of a normal webpage (as I was in the first two examples), the contents tab would simply show me the listing for that folder (not the one containing it).

What The Contents Listing Shows

• Checkboxes - used to select one or more pages, for which the buttons on the bottom can be used.  The very top most checkbox selects or deselects all of the checkboxes.
• Title - Simply the title of the page.  If the title was never supplied, Plone will use the "shortname" (explained in the Plone 2.0 Quickstart tutorial).  (This frequently happens when a page is inadvertently created, but never filled out.)
• Size - This is the filesize, usually small for documents, but larger for PDFs, and possibly very large for images. Generally, images shouldn't be larger than 20 KB or so, to prevent inordinate download times for dialup users.  You should save your images so that their file size is as small as possible.
  
• Modified - When edits were last made to the page.  Don't let the military time throw you!
• State - The publishing state, as explained in the previous page.
• Order - The pages are listed in the order in which they were created (unless you moved them around), and that's how they will appear in the navigation.  The Order column has two arrows for each page; click on them to move a page up or down in the sequence. 

• Rename - While you can rename a page when you're in the Edit tab, this button allows you rename more than one page at a time.  You can change the title and the short name.
  
• Cut - Just like in Windows Explorer, this allows you to move one or more pages.  After selecting which pages and hitting Cut, a Paste button will appear in all subsequent folder listings, allowing you to navigate anywhere in the site and paste those pages.  Note that pages will not move until you actually hit Paste, so you will never lose anything by using the Cut button.
  
• Copy - Copy is just like Cut, only it creates a copy of the original page, instead of moving it.  After hitting Copy, a Paste button will appear just as with Cut.  Note that Paste will paste only the most recent item(s) that you copied or cut.
  
• Delete - Very straightforward, this button deletes all checked items.  (Although as explained in the undo section, this shouldn't necessarily be permanent.)
  
• Change State - This is lets you change the publishing state for more than one page at a time, including also the option to change the state for the contents of subfolders.  This can be a handy time saver if you are drafting a lot of content at once.