What does breakat&vim mean?

Question

I'm trying to understand this SO answer. The snippet reads:

:set nolist wrap linebreak breakat&vim

Answer 1

It resets the breakat option to the Vim default: ^I!@*-+;:,./?.

Where ^I stands for the tab character.

You get the corresponding help paragraph with the :help :set-default command.

:se[t] {option}&    Reset option to its default value.  May depend on the
                    current value of 'compatible'.
:se[t] {option}&vi  Reset option to its Vi default value.
:se[t] {option}&vim Reset option to its Vim default value.