As i understand it, it is simply confirming something that was expected. E.g. Two people are at a bus stop waiting for a bus scheduled to arrive at noon, and just state the obvious "It is noon, and here is the bus!" when it arrives.
"Itt", "ott" and "hol" are interesting, because if they are in front of the noun, "van" is not obligatory.
- "Hol a busz?" = "Hol van a busz?"
- "Itt a busz." = "Itt van a busz."
- "Ott a busz." = "Ott van a busz."
But this is only valid for singular. In plural "vannak" is always necessary with locations.