He goes to a wedding and His mother Mary is there. Scholars tell us that most likely the bride and groom were relatives of Our Lady. We know the couple was from a poor family because they ran out of wine. And so Mary goes to Jesus to ask Him to help. Jesus does so. He turns water into wine.
It is His first public miracle, and it took place at a wedding, pointing to the sacredness of marriage. Jesus performs this miracle at the request of His Mother, pointing to the importance of Mary's intercessory role, which we hold so dear today, to Jesus through Mary.