Parameters of the universe are currency. Time is one of them, space (or area on earth’s surface) is another, and energy is a third. How these three things are used is what generates
value to human beings. Each of the fundamental items can be traded individually, but money is used as a proxy for
value. The most common trade is when a person can trade their time and their body’s energy. They produce some level of value using those two inputs, and receive money (a proxy for that value) in exchange. A person who can generate more value with the same amount of time and energy should be receiving more money than someone who generates less value, as money is only a proxy for value.
People can also secure space. We’re used to thinking in terms of real estate, which always prices in the value of a structure or natural resources or potential on top of the raw spatial resource. But the raw three dimensional space can be traded as well, just like time or energy, as it is finite for humans.
Money is just a tangible abstraction later on top of these fundamental parameters of the universe we trade. Providing lots of energy in a small space in a short period of time is incredibly valuable to humans, and so money reflects that. Using energy and time and space in a more efficient way to produce something in a factory is valuable, so money reflects that.
It’s not that money isn’t real currency, it’s just an abstraction layer for tradable natural commodities like time, and energy, and space.