Traders found that they had certain goods that were valued everywhere and that there was always a market for them. Those goods became a medium of exchange. Money is anything that is generally acceptable in exchange for a good or service. When money began, it was an item that a trader knew would be accepted by others. Money could be livestock, corn, salt, spices, gold, silver, etc.
Money is a medium of exchange.
That is what makes it different from other assets like stocks, bonds, land, or buildings. A medium of exchange is anything that is generally accepted as payment for goods and services. When we used corn, salt or spices that is commodity money. Commodity money is when something is a consumable item as well as a medium of exchange. The earliest money was commodity money.