One of the roles of money is to be a medium of exchange. This is usually explained in contrast to the barter system. Bartering is to exchange one type of good for another without the use of money. The problem usually pointed out is that a unit of one good is not equivalent to another unit of good. Clearly, trading a cow for a dog is not the same thing. And you may not want ten dogs for the one cow.
So money, something with a designated value to be use to facilitate the exchange of goods, is a simple solution. And when no hard currency is available something else may stand in for money. For example, during the war in prison camps cigarettes become the currency for exchange. Human Beings have the capacity to place abstract value on things for purposes other than their intended use.
I would like to point out again that money is used for the act of exchanging goods. These two italicised words are important because they cover up something not made obvious by their meaning.
Good or goods are contentious words in that firstly the choice of form to represent items has the positive connotation of “right”. Might have chosen bad and bads to represent items for exchange it may have said something how we feel about them. These are things we want. They are good for us that therefore a good. Turning an adjective into a noun is a brilliant stroke of linguistic self-deception.
The other word, exchange, is also deceptive but for different reasons. It involves an assumption, the assumption of ownership. You might say, “but so what”. It is the unquestionability of ownership which is worrying. That tree in the forest is firstly assumed to belong to someone, if it is on land not owned by someone. Thus that someone is always a human being. Yet, the land is home to thousand, millions, billions of individual life forms that depend on it for survival. The tree itself is a life form. The act of taking ownership of the tree, firstly, is to treat it like a lifeless object. It becomes a good or commodity. It becomes something tradable, something for exchange. Secondly, it is to place it, as a life form, into slavery. (As a side comment, this perhaps why we so easily can put people into slavery as well, because we can objectify living things with words, names, labels.)
Exchange also assumes to be exchange between people, not between people and animals or animals and animals. Other living things are assumed not to exchange. In a sense animals share, which humans seem not to understand. The assumption that something is not claimed means it is not owned by anyone is circular logic that thing need to be owned to have value.