Local events, those for a city or region (milongas, prácticas, classes), go live right away.
International events, such as festivals and marathons, are reviewed by an administrator before they are published.
It is not a rule tied to type alone. It depends on whether the event has a region.
If you save a draft, the same rule applies when you publish it.
Event states are: draft, in review, published, upcoming or past, hidden and cancelled.
Claiming an event that already exists is separate: you can, and it does not send the event to review. That is in Claim an event.