Before money was used, people got what they needed and wanted through trading. Farmers grew crops and could trade their food for pottery, cloth, and other goods in the city. The workers in the city could get the food they needed by trading the things they made with farmers.
Traders would bring materials from other places. Goods that were traded included metals, clay pots, shells, beads, and stones (such as for jewelry or things like a flint rock for starting fires). If a trader came from far away with something like green jade from China, then what they had would be very valuable as it would be very rare. Traders could move lots of goods by floating them on a boat. Their boats could be made of wood or even just bundles of reeds.
Archaeologists have found thousands of seals in the Indus Valley. It’s a small, flat piece of stone with a carving in it. It could be pressed into clay to leave a mark that would harden. Think of it like a tag on your clothing naming the brand that made it. The potter could show that it was his work, or someone could mark something to show that it belonged to them. Here are some seal examples. We don’t know how to read their writing, but there is obviously some writing on there as well. The most common animal on a seal is the unicorn.
Indus Valley seals have been found in Mesopotamia showing that they traded there. Here’s a map that shows where traders might have gone. These are some of the earliest civilizations. Look at the map and think about what their trade routes might have been.
Trade wasn’t always about getting what you needed. Here’s an item that might have been traded. This is jewelry from Mesopotamia at the time, though the Indus Valley would have had its own gold jewelry. In the Indus Valley, jewelry included not only earrings like what is pictured, but necklaces, brooches (pins you wear), and bracelets.
Public domain unless noted below
Exhibit: Biswarup Ganguly [GFDL, CC BY 3.0], from Wikimedia Commons