Money does not exist. Money is ‘frozen’ value: values are created and exchanged for money, which money in turn is then used to exchange for more values.
Step 1: Values are created, then get transacted to someplace other than their creation-point. The value moves somewhere else, leaving a “value vacuum” behind it. That vacuum is filled in temporarily by money.
Step 2: That money that filled in the vacuum is then pushed out to cause new external values to flow into the vacuum, thus filling it again.
Values themselves are not money, nor is money value, or even valuable. Money is the stand-in for the transactable nature of values. Money is a placeholder, like the “0” in mathematics. “0” is not a number, but a placeholder for orders of magnitude. Money acts like this, although there is an imperfect relation between money as placeholder and the values-vacuums it attempts to temporarily fill; namely, the eventual values that come to fill the vacuum are usually not a perfect match for the values that left and originally caused the vacuum. Also, vacuums overlap, and change all the time, and are nebulous.
Marx and Adam Smith noticed that values are either used or exchanged (use value or exchange value). A value is “used” when it is exchanged for something one wants, a direct values transaction without the need for money; a value is exchanged when it is simply traded out for a value-vacuum into which some quantity of money comes. I would re-interpret Marx’s terms in so far as the only time values are truly “exchanged” is when it is for money, and any other time there is a value-to-value exchange this is technically use value going on.
Surplus value is what happens when values are put to use to create more value than was originally there. This happens traditionally in labor, where workers create values that pile up and eventually contribute to enough values-exchanges to where new additional values are acquired, and/or these created values are exported from the value-creating point in order to produce a huge value-vacuum into which money flows. Surplus value is also created with increases in efficiency, in technology, and in acquiring new resources, since these things either refine the value-making process or reach out and grab values-to-be that were laying around and not yet converted into true (human) value for use or exchange.
Bottom line: money does not exist. Only values exist. We think money exists only because we already know that values exist.