The wedding breakfast is a dinner given to the bride, groom and their guests at the wedding reception.
The phrase wedding breakfast dates back as far as 1838, and it is reported that the bride and groom would fast before the wedding in order to be eligible to receive the sacrament of Holy Communion. After the ceremony the priest would bless and distribute wine, cakes and sweetmeats which would break the fast for the newly married couple.
Nowadays the wedding breakfast is usually served mid-afternoon, and does not look like a typical breakfast so the name can be confusing.
However, as it is your first meal together as husband and wife it surely acts as the breakfast of your marriage.