Store of Value, which means people can save it and use it later
Unit of Account, that is, it provides a common base for prices
Medium of Exchange, something that enables people to buy and sell from one another
While crypto currencies do not necessarily meet all of the definitional requirements at the moment, they do represent a natural evolution of money. Additionally, many of the most appealing aspects of crypto currencies attempt to address many of the issues that have plagued money throughout history.