Maid of Honor
Out of all her attendants, the bride relies most heavily on her maid of honor. Traditionally, the maid of honor is the bride's sister or closest friend. FYI, a married honor attendant is technically referred to as a matron of honor, but that has taken a back seat in recent popular vernacular.
Before the wedding, the maid of honor's duties include coordinating the bridesmaids' activities, such as meeting for a dress fitting and organizing the bridal shower and bachelorette party. She also helps the bride and groom with any preparatory errands or tasks, like addressing the invitations and keeping records of gifts.
On the wedding day, the maid of honor helps the bride dress and accompanies her to the ceremony. She signs the marriage license as the bride's witness, arranges her veil and train during the processional and recessional, and holds her bouquet at the altar. At the reception, she dances with the best man and organizes the bridesmaids for formal pictures. Before the couple leaves for their honeymoon, she helps the bride change, and makes certain her dress and bouquet are kept safe until she returns.