Before there was money, people in Sumer would barter for what they needed. Two people would trade goods with each other. For example, a farmer might trade a bushel of wheat for a new pot.
Bartering is difficult because trades can become too complicated, so Sumerians started using barley as a form of money. Workers were paid in barley. They could use the barley to make bread or beer, or they could trade the barley for other goods. This system was better, but it was difficult to transport a large amount of barley. It could also spoil.
Sumerians ended up using silver as money. People would keep silver in bars or shape the silver into coiled bracelets. When they wanted to buy something, they could hand over a bar or break off a part of the bracelet.