How do you find what command a toolbar button represents?

I'd like to import the function of some of the tool bar buttons on the "Reviewing" toolbar into a customized "Reviewing" menu. It turns out that I use some of the buttons on the "Reviewing" tool bar quite frequently, but the rest almost never. So, by importing these frequently used functions into a newly built menu, I will be able to claim more real estate for text editing. But the problem is, I don't know what "command" these toolbar buttons represent. I wish there was a "property" menu when you right-click a toolbar that displays such information.

Is there any easy way to find out what command a particular toolbar button executes?