Fiat is money that is made by government regulation or law (Wikipedia). If you spend any time around bitcoin fans you will hear the word Fiat.
A lot of people in the bitcoin/ crypto currency space started studying economics after the 2008 crisis. I didn’t really find bitcoin till 2013 right when the price spiked to $1,000 USD (and from there the price dropped slowly down to $250 USD).
Asking questions about economics and money should lead to a bigger questions. Where does money come from? How much money is out there? How much money is being created monthly, yearly? What does money creation do to the value of your money?
I wonder where your study of money will take you.