Cryptocurrency is a digital asset that uses strong cryptography to secure transactions, any type of information and verify transfers. It is a decentralized system. So, it is different than central banking systems.
Since the banking history has economical recessions from time to time, people needed to have an asset that centralized banking system cannot control. After the mortgage crisis in 2008, Satoshi Nakamoto, an anonymous person or group, has came up with Blockchain technology. Using blockchain technology, the users help to improve the system and earn cryptocurrencies in turn.
As a result, cryptocurrency is a new currency coming after banknote money. People will not need to carry paper money anymore and have cryptocurrencies to make payments.