  We review different classes of cryptocurrencies with emphasis on their
economic properties. Pure-asset coins such as Bitcoin, Ethereum and Ripple are
characterized by not being a liability of any economic agent and most resemble
commodities such as gold. Central bank digital currencies, at the other end of
the economic spectrum, are liabilities of a Central Bank and most resemble
cash. In between, there exist a range of so-called stable coins, with varying
degrees of economic complexity. We use balance sheet operations to highlight
the properties of each class of cryptocurrency and their potential uses. In
addition, we propose the basic structure for a macroeconomic model
incorporating all the different types of cryptocurrencies under consideration.
