[The whole ⌥ Option key vs. Alt thing...]

@Russ Johnson that's a great explanation. I'm always discovering new stuff about Macs (tried the option-resize stuff in Sierra and it still does all sorts of neat stuff. I would add that the key is also used to access hidden/administrative preferences and utilities or different right-click menus.

 

What's annoying is that many current Macs have "alt" written on the keyboard and the "option" symbol, but do not have "option" written on it. This is the case on my Canadian multilingual keyboard (I do a lot of translation) and others I have seen.

 

I think many people read official and non-official forums and help files are left searching for the "option" key when following instructions—it's not intuitive.