Macro buttons allow you to do sets of button combinations by pressing a single button.
For example; say you have a combination of a-x-a-x-a-a-right trigger. You could assign that to the white button and then when you press the white button it will automatically do that combination.
The macro button is purely for convenience.
Read the instruction manual to figure out how to work it, you'll probably have to fool around with it a bit to get it right.
I do know this - xenforo dropped the ball by not keeping the vbulletin reputation comments as a feature. The loss of the Reputation comments data when we switched to Xenforo really was the death knell for the site when it came to all the users that left. I know I missed it so much and I got way less interested in the site when that feature was gone and I run the site.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory