The following information is taken from Wikipedia:
A puzzlehunt is a puzzle game where teams compete to solve a series of puzzles at a particular site, in multiple sites and/or via the internet. Groups of puzzles in a puzzle hunt are often connected by a metapuzzle, leading to answers which combine into a final set of solutions. Some famous annual puzzlehunts are:

• MIT Mystery Hunt (Cambridge, Massachusetts, USA), the first of its kind
• Microsoft Puzzle Hunt (Redmond, Washington, USA)
• Miami Herald's Tropic Hunt (Miami, Florida, USA)
• Maze of Games (Indianapolis, Indiana and Columbus, Ohio, USA)
• Manbites Dog Theater PuzzleHunt (Durham, North Carolina, USA)
• Google Puzzle Hunt
• TMOU (Brno, Czech Republic)

College puzzlehunts include the aforementioned MIT Mystery Hunt as well as:

• The Paperchase at Cambridge University
• PuzzleCrack (University of Illinois at Urbana-Champaign, USA)
• UT PuzzleHunt (University of Texas at Austin, USA)
• Melbourne University Puzzle Hunt (University of Melbourne, Australia)
• PuzzleQuest (Carnegie Mellon University), hosted by Microsoft
• Puzzle Challenge (Multiple Locations, North America), hosted by Microsoft as a recruiting event on college campuses.

Treasure Hunts
There are many different types of treasure hunt games which can have one or more players who try to find hidden articles, locations or places by using a series of clues. This is a fictional activity; treasure hunting can also be a real life activity. Treasure hunt games may be an indoor or outdoor activity. Outdoors they can be played in a garden or the treasure could be located anywhere around the world.

A puzzlehunt is a typical treasure hunt game involving clues. Sometimes though a hunt may not have clues because of the age of the children. An Easter egg hunt that is performed on a day near Easter Sunday. Young children just search for as many eggs as they can find whilst older children may have clues to one egg.

An armchair treasure hunt is any activity that requires solving puzzles or riddles in some easily portable and widely reproduced format (usually an illustrated children's book), and then using clues hidden either in the story or the graphics of the book to find a real treasure somewhere in the physical world.do not try this at home - although it seems to be for children, this genre is really for dedicated adults.

Adult treasure hunts are becoming increasingly popular (different types are listed below), as are many other forms of organized adult entertainment like trivia nights, video game tournaments and adult sports leagues. Some theorize this is due to the extended adolescence. Others cite the difficulty in meeting new people with the breakdown of traditional community organizations.

Geocaching is an outdoor treasure-hunting game in which the participants use a Global Positioning System (GPS) receiver or other navigational techniques to hide and seek containers (called "geocaches" or "caches") anywhere in the world.

An armchair treasure hunt uses a book or a puzzle as basis, in which clues are hidden. This type of Treasure Hunt normally takes months to solve and has immense prizes to be won.

Letterboxing is another treasure hunt game. It is played outdoors and combines elements of orienteering, art and problem-solving. Letterboxers hide small, weatherproof boxes in publicly-accessible places (like parks) and distribute clues to finding the box in printed catalogs, on one of several web sites (see below), or by word of mouth. Individual letterboxes usually contain a logbook and a rubber stamp.

More recently, the treasure hunt game has been used for corporate entertainment and team building. Organizations may use treasure hunt games where managers perceive that inter-departmental relationships need to be improved. Alternatively it could just be a morale booster.