Paper Money is a Promissory Note
One is to One
Backed by Gold.
That is those were the days.
Now..?
Sorry.
Paper Money is Fiat Money
Not backed by Gold
In fact, not backed by AnyThing.
One individual and his family together with about 300 most famous influential people in the World
They print as many as they want.
In fact, they have printed Trillions thus far.
Its one piece of paper is worth almost nothing soon.
A Candy Bar using Fiat Money may cost 100 Trillions Dollars.
This has happen before.
Either going shopping one need to drive a lorry of Fiat Money
Or bring this one piece 100 Trillion, the value may be $ 0.10 cent or less.
An Individual and a Group of Individuals know this and said, "If those 300 can print as many Fiat Money as they want, and place only digits through their central banks, we too can do the same and issue Digital Currency out of thin air."
Nations bankrupt..!
It was in one fine year, 2008, Satoshi Nakamoto made the announcement, He has found a way solving the problem of Currency Exchanges. It is Peer-to-Peer, without any Central control, thus Decentralized, and no the same one piece Money can be issued as twice,.
BitCoin.
At present BitCoin is position equivalent to a USD.
For example 1 BitCoin = 1 USD.
But that is years ago.
Today 1 BTC = USD 9,017.474061
Some say there will be a time when 1 BTC is not equivalent to USD any more.
If and when the value of USD is 100 Trillion a piece enough to buy a Candy Bar.