A referee is the person who can decide what the result of a game is if the players cannot agree.
From a referee you can expect in depth knowledge of the rules
There are many famous refereesí decisions and they are have often been contested, especially if there was misunderstanding about the rules of the game.
It is interesting to know if under tournament rules? the referee is passive (only act if asked) or active (can also act without being asked)
Other rules also allow referees to decide the outcome. An example in CGOS: the referee program decides if its superko rule is broken. without any player having to claim it. Maybe this is because it is a computer go tournament and the Go Text Protocol has no standard claim routines.
willemien just found this page missing. Maybe go-players don't like referees.