Before money existed, trading required something surprisingly hard to pull off: finding another person who happened to have exactly what you wanted, and who also happened to want exactly what you had. Economists call this the "double coincidence of wants," and it's the core problem money was invented to solve. A farmer with extra wheat who needed shoes had to find a shoemaker who specifically wanted wheat that day — otherwise, no trade happened at all.
Money works because it does three jobs at once: it's a medium of exchange (something everyone will accept in trade), a store of value (something that holds its worth so you can save it for later), and a unit of account (a common way to measure and compare the value of totally different things, like how many hours of work equal one bicycle).
Insider Angle: money has taken wildly different physical forms across human history — cattle, salt, cowrie shells, and precious metal coins all served as money before paper currency existed. The English word "salary" is widely believed to trace back to the Latin "salarium," linked to "sal," the Latin word for salt — a reminder that pay itself has been tied to whatever a society trusted as money at the time. Today's U.S. dollar is "fiat" currency: it isn't backed by gold or any physical commodity, only by government backing and the shared trust that everyone else will accept it too. That link to gold wasn't always absent — President Nixon severed the dollar's last formal tie to gold in August 1971, a moment sometimes called the "Nixon Shock."
Try This: Try to imagine trading for everything you need this week using pure barter, with no money at all. List three trades you'd need to make and how hard it would be to find the right person at the right time for each one.