Cryptocurrencies are purely digital forms of non-fiat currency, also referred to as altcoins. That means that they are not physical coins nor are they backed by banks or governments. Bitcoin is the best-known cryptocurrency, with Ethereum’s Ether as a close second. As a consequence of the design and utility of these currencies, they have consistently been the most valuable and most traded currencies on exchanges.
WHAT IS CRYPTOCURRENCY?
Let me begin by saying, just the way you have physical money(fiat currency), crytocurrencies are digital or online money which can not be seen with the physical eyes like paper money but it's represented with figures and symbols.
That doesn't make them less money; they are accepted all over the world as a means of payment. Paper money is called fiat currency while digital money is called cryptocurrency.