An Item is one of an Item Type.
You can have many items that are all of the same item type, like many of one material or product.
Each Item has its own unique Item ID, like a serial number or license plate.
You can see items in different ways, such as a list of items a certain Item type at a location:
If you click on one of these items, you can drill down to see its details:
... and its history:
At any time, you can use the built-in Search tool to enter or scan an Item ID to look for it and then see its complete history: