Currency/money is a data-structure for a kind of cooperation algorithm. That is the way to understand it in an informational world. Note that money is not really about being a 'medium of exchange', a 'unit of account', 'store of value' -- those are tautological ways to look at it, they are its particular forms of activity, the real purpose is cooperation (more) generally.
The radical thought is that we do not really want currencies. We want something more information-rich -- something made for our current information tech, rather than originated from cowry shells or whatever. Hardly anyone is thinking in this way though, disappointingly. Yet it is myopia: if you look around non-currency systems are beginning to evolve. What is reputation, or 'karma', are they currency? Not really. What are things like Flattr and Kickstarter, are they markets? Not really.
Start deliberately thinking beyond currency.