Cryptocurrencies can be transferred between people without using an intermediary, like a bank. Cryptocurrencies can be bought peer to peer, through online exchanges or by participating in Initial Coin Offerings.
Bitcoin is the most well-known cryptocurrency. However, thousands of cryptocurrencies are available in the digital market right now. Ethereum, Ripple and Litecoin are other well-known examples.
Cryptocurrency is treated as property for tax purposes. There are no special tax rules for cryptocurrencies - ordinary tax rules apply.