What is this series of codes in little squares that Word displays on pressing the Alt key or some key combinations? And what for?
Thanks for any help.

SerieCodigosWord.jpg

These are the Alt keyboard shortcuts that are a part of the Ribbon Interface.
By pressing the keys shown, you will activate the control.
Use the keyboard to work with the ribbon - Office Support

Thank you, Charles; clear and useful information.
But, to be honest, I fail to see the rationale behind this function as, in my Word at least, each of those actions is already identified, and more clearly, by an icon or by the name of the tag; so these little squares seem to do nothing but superimposing a number or letter on them, rather messing the previously neat appearance of the ribbon. Is it so?
ACA

The purpose, as set forth in the title to the link, is to let you access those functions without using a mouse.

There are letters for each tab. Note that Insert is N rather than I.
The first level is the tabs and the Quick Action Toolbar buttons.
If you select a tab, you then get more letters/numbers for the controls on that tab.

If you are a touch typist, these can be much faster than using the mouse / touchpad.

If you customize the Ribbon or QAT, those modifications also receive these shortcuts.


Here is the Standard Ribbon/QAT in Word 2019:



Here is my customized Ribbon & QAT:

By the way, your profile is showing Office 2007 but your screenshot is from Word 2010. Please consider updating your profile. You'll get better answers that way.

Thank you again for patiently explaining.
I wasn't aware of all that; but after reading your post I'll try commanding through typing for with the touchpad I am not very nimble.

And I just updated my profile for Windows (10) and Office (10); thank your for that too.
ACA

You are welcome.