“The best man is the chief male assistant to the bridegroom at a wedding. In North America and Europe, the groom extends this honour to someone who is close to him, generally either a brother or his closest male friend. When the groom wishes to give this honor to a woman, she may be termed the best woman or best person, or may still be referred to as the 'best man'. The bride's equivalent of the best man is the maid or matron of honour. A gender-neutral term is honor attendant.

While the best man's required duties are only those of a friend, in the context of an American/British white wedding, the best man will typically:

• assist the groom on the wedding day,
• keep the wedding rings safe until needed during the ceremony,
• act as a legal witness to the marriage, and
• make a toast to the bride and groom at the reception.
• be responsible for organizing the bachelor party or stag night as it is known in the UK and Australia.”

(Source : Wikipedia)