Hey there!
An oligarchy is/was a powerful from of government. It was ruled by any sort of group of powerful people - aristocrats, wealthy landowners, or anyone that had lots of money, power, and influence.
Often in ancient times, they were aristocrats. They made laws that benefitted themselves and the trend was often that the poor lost more wealth, and the riched gained more - as oligarchs passed laws to benefit the rich.
Some argue that even today, countries like Russia and those that don't have a complete democratic or republican government have oligarchs, although that's always arguable.
Hope this helps!
