No currency has changed hands. Increasingly today people get paid simply by receiving notice that the payor has sent the person's numbers directly to the bank. Of course, it is not just checking accounts that have numbers. People have money in savings accounts and 401k's. People can write checks against their brokerage accounts where there are numbers saying how much their stocks and bonds are worth.
Some people can even write numbers on an account that has numbers for the value of their house.
People use credit cards to move numbers around. And, of course, with the advanced financial technology of today the financial institutions that keep track of all these numbers are happy to let people write numbers that they don't have yet. All the person has to do is agree to payback the numbers in the future plus interest. And for all these numbers, vendors will give you things you want - gas, brain surgery, hair styling, cats, whatever. Now if you thought creating money by cutting up old newspapers would be easy, think how easy it is to write numbers.