Currency is usable if it is a store of value, or, put differently, if it can reliably be counted on to maintain its relative value over time and without depreciating. In many societies throughout history, commodities or precious metals were used as methods of payment because they were seen as having a relatively stable value.
Rather than require individuals to carry around cumbersome quantities of cocoa beans, gold, or other early forms of currency, however, societies eventually turned to minted currency as an alternative. Still, the reason many examples of minted currency were usable was because they were reliable stores of value, having been made out of metals with long shelf lives and little risk of depreciation.2
In the modern age, minted currencies often take the form of paper money which does not have the same intrinsic value as coins made from precious metals. Perhaps even more likely, though, individuals utilize electronic currency and payment methods. Some types of currencies rely on the fact that they are “representative,” meaning that each coin or note can be directly exchanged for a specified amount of a commodity.