There is a long-standing tradition associated with holing out from the tee which can make it a costly achievement depending upon the venue.
A hole- in-one occurs when the ball is hit from the tee into the cup and stays there. (The last bit might seem a tad pedantic, but I know of one chap who hit the ball into the hole on the full, but it bounced out and rolled into a greenside lake.) A hole-in-one is also known, albeit less commonly, as an ace.
To count as a true hole-in-hole a couple of criteria have to apply. The first is that you are not alone; you can be playing alone, but someone has to be there marking your card to testify to your feat. The second is that it is part of a formal round of golf, not just part of a few practice holes.
Golfing tradition dictates that any golfer who makes a hole in one buys the drinks afterwards. Who he buys for can vary upon whatever local tradition exists as the club. The most widespread one is that the golfer buys a drink for his playing partners after the round and also a drink for everyone else in the clubhouse or bar when he returns.
Thus a hole in one can become mightily expensive if you happen to hit a busy time in the bar. Some people therefore believe it acceptable if the hole-in-oner only buys for his playing partners, but others look deeply askance at such an attitude.
However some clubs have a local policy such as that the golfer puts some money behind the bar by way of a tab and when that is used up, that is the end of his obligation. Others have a tradition that the player just buys a large bottle of whisky which then sits on the bar counter for anyone to help themselves to a tot from.
Some insurance companies offer hole-in-one insurance whereby the maker of a hole-in-one gets a stated pay out by the company. Often this is bundled in as part of a more general golf accident insurance policy.