If you never work with mouse for your Excel work, I believe your are a true master in using F6.
If you use both mouse and keyboard like most people do, you may probably know little about F6.
However if one day your mouse refuses to work, you will regret for not knowing what F6 does.
So what F6 does? Take a look at the following screenshot captured from support.office.com
Got it?! No way…
In order to understand what it means, let’s understand the terminology first:
For demonstration purpose, I have started with Split Panes so that you will better understand how F6 key helps you navigate when there is Split Worksheet.
Let’s start by activating the upper right Pane (1) of the worksheet. To activate Pane (1), click inside that pane (yes, by using mouse).
Now Pressing F6, it takes you to the next Pane (2)
Now Pressing F6 again… 
And again…
And again… it switches to Clip Art
This is tricky. Normally you won’t have Clip Art or Selection Pane on your workbook. I called for them intentionally for demonstration.
By the way, you have to have EXCELLENT eyesight in order to notice the activation of the Clip Art pane.
Now let’s press F6 again… it takes you to the next “Task Pane“, i.e. Selection Pane in the example.
Note: Once your focal point moves to the pane, you may navigate the items within by arrow keys. Use Tab key to jump over to different buttons; Enter or Space bar to enter.
And F6 again… This is another eye test indeed: 
Do you really see the tiny difference? You have just switched to the Zoom Control. Now you may change the page layout or zoom level by using keyboard only…
Next F6 press would take you to the Ribbon…
Notes:
- If you do not have Split Worksheet and Task Pane(s), pressing F6 twice would take you to the Ribbon.
- Another direct approach to go to the Ribbon is the Alt key. A single stroke of Alt would do.
- When you switch to Ribbon, you may navigate by the shortcut keys displayed; or by using arrow keys. Please note: Once you used arrow keys, all the hints of shortcut key will be gone.
With one more F6 press, the cycle completes.
Do you notice that the F6 key takes you to different areas of Excel windows in a Clockwise direction?
Shift+F6 does the same switching but in reverse order (Anti-Clockwise).
The “official” description of Ctrl+F6 should be clear enough – it switches between opened workbooks. 
Although I showed you the sequence of the switching in the above screenshot where there are four workbooks opened, don’t mind it too much as it may change when you save one of the workbooks. It may be easier to pay attention to which workbook has been activated while pressing Ctrl+F6.
Ctrl+Shift+F6 does the same thing in reverse order. The Shift key performs this behavior most of the time.
Tip: A better alternative to this shortcut would be Ctrl+Tab
I hope now the following makes sense to you.
If not, how about the following “rephrased” points? Are they any better?
- F6 alone – Switches between different “toolbar” (I think this old term can be understood more easily) and worksheet panes
- Shift+F6 – Same as above but in reverse order
- Ctrl+F6 – Switches between different opened workbooks
- Ctrl+Shift+F6 – Same as above but in reverse order
Note:
The shortcut combinations stated above have been tested with Excel 2010. If you find it doesn’t work in other version of Excel, please let us know by leaving your comment.
Also feel free to share with us your tips in using F6.
For other Function keys:
