Bride is a new female-only class that features in Fire Emblem: Awakening and can only be obtained as downloadable content as a reward for completing Smash Brethren 2. As its name suggests, characters of the class wear a bride's wedding dress. DLC Eirika starts off in this class and any female character can access this class by using a Wedding Bouquet when they're Level 10 or over (or any Level, if in a promoted class).
The Bride class is treated as a base class in terms of its Experience Point gain calculation when fighting and defeating other units, despite the class having the stat caps of an advanced class. This enables a unit promoted to the Bride class to gain levels (and therefore stats) at a much faster rate than other advanced classes when fighting units of the same caliber, while allowing them to be on-par with advanced classes stat-wise.
Additionally, a unit promoted to the Bride class can only reclass into a base class at lower levels. However, like the Villager, Manakete, Taguel, Lodestar, Conqueror, Dread Fighter, and Dancer classes, if a character is reclassed at level 30, then they can reclass to promoted classes as well as base classes.