A man who is engaged to be married is called his partner's fiancé; a woman similarly engaged is called her partner's fiancée.
Once a wedding date has been set the banns of marriage, commonly known simply as "the banns" (from an Old English word meaning "to summon") are announced. This is a notice, usually placed in the local parish church or registery office, which tells everyone that a marriage is going to take place between two people.
The purpose of banns is to enable anyone to raise any legal problems as to why the two people shouldn't get married, basically it is to prevent marriages that are legally invalid. Impediments vary between legal jurisdictions, but would normally include a pre-existing marriage (having been neither dissolved nor annulled), a vow of celibacy, lack of consent, or the couple's being related within the prohibited degrees of kinship.
In England, a marriage is only legally valid if the reading of the banns has taken place or a marriage licence has been obtained.