Think of your younger days when Mom left a blank shopping list on the refrigerator door. If you opened the fridge and saw the milk was running low or you opened a cabinet and something was missing, you'd put the item on the list. Mom would take the list to the store and buy what was on the list (including the ice cream you stuck on the list).
In the business context, people are walking around and noticing products and services that need to be purchased. You start with an employee who wanders by a parts cabinet and sees a part is missing. She scans the QR code which takes her to a list of parts that should be in that cabinet (after authorizing the user of course). The user adds the missing part to a shopping list associated with the cabinet or the buyer who processes orders for the cabinet. She doesn't have to know any of the accounting. The power user is notified that an item needs to be procured and can decide to take immediate action or if the purchase can wait. When the power user makes the purchase, she goes to SRM or ERP, accesses the shopping list, adds items from the list to a shopping cart or requisition, supplies the needed information (eg: accounting), and orders the product(s). It's a great way for employees to make the requests they need without having to know all the accounting.