Used as a reply in certain contexts when someone has
just said
something quite verbose or confusing. "Bless you" can be used in the same
way in this sense. Not all native speakers of English use it.
From the A Way With Words (waywordradio.org) radio show, Aug.
23, 2010:
Grant Barrett: "It's the second
person singular indicative present of the verb 'to see', s-e-e."
Caller: "Gesundheit."