The Second Estate was one of the three dividing bodies in France that had originated in the Middle Ages. The nobles were the members of the Second Estate, and could be either nobles of the sword or nobles of the robe. The Second Estate had many of the same privileges as the First Estate, but did not have nearly the number of ties to the Third Estate as the First did (many members were born into the Second Estate).
A common misconception involving the nobles is the idea that all were fabulously rich. While it is true that many were very rich, there were also many who were less affluent, sometimes reaching the financial levels of an average member of the Third Estate.
Nobility, along with the privileges that went along with it, was abolished during the French Revolution, but was reinstated during the reign of Napoleon Bonaparte.
Most information from lectures by professor Storch at the University of Wisconsin - Rock County. Additional information from Fourth Edition Western Civilization from 1300 by Jackson J. Spielvogel.