There is no society with any sort of industry, imports and exports, or connection to the modern world that does not find conveyor uses invaluable. Although this technology was not brought into practicality until the twentieth century, the idea behind it is ancient. Many people knew that a group of individuals could do more transporting of a commodity when each one stood in place and passed the item to the next person.
Think of stevedores unloading freight. The man in the ship does not hoist the bag or bale onto his shoulder and clamber onto the dock. He passes it to one already on land, who often hands it off to another. People fighting a fire fill buckets and pass them along a line in order to speed up delivery.
A conveyor was first used in the mining industry, which today has the longest ones in existence. A moving belt is the easiest way to move loose ore up from underground and then to storage piles and loading areas. Trucks and railroad cars are also loaded by moving under hoppers or chutes filled by the same method.
Basically the system is a loop of material that is pulled along between two pulleys, rotates over the end, and goes back underneath to begin the process over again. One or both pulleys will be powered by an electric motor (although many areas without electricity use another fuel.)