Old Vs. New money refers to a system of classifications for wealth. "Old Money" families are families who have steadily built their wealth over generations. "New Money" people are either individuals or groups that have acquired wealth over the course of a few decades. Societal views on the two classes of wealth differ. (Below, left: European Nobility's wealth often predates recorded history)
Old money is what usually comes to mind when people talk about wealth. The "old money" idea is one that stretches back to the medieval period. Prestigious titles, trust funds, and titular buildings (ex: Rockefeller Center) are the hallmarks of this class. Old money families include the aforementioned Rockefellers, the Carnegies, and the Vanderbilts. You may notice that each of these families first began accruing wealth during the Industrial Revolution. Rockefeller came to monopolize the oil business, and Carnegie founded a Steel Industry giant from almost nothing in the same era. Most non-European nobility families of this class owe their wealth to an Industrial entrepreneur.(right: Rockefeller Center)
The New Money class includes the likes of Bill Gates and Oprah, people who have risen to fabulous wealth mostly independently. This also applies to families with comparatively young generation-spanning wealth, such as the Hiltons. It is likely that as times goes on, said individuals will produce dynasties that will become Old Money families. How long this will take cannot be precisely determined, as their is no set number of generations a family must enjoy wealth before being considered "Old Money"(Below: Bill Gates)
Information thanks to 123helpme.com.