The Inventory feature will be used for the Store Seller.
In Inventory system a company tallies up their inventory stocks every once in a while. Or periodically. Then they compare a current number against a previous number to determine inventory change over time.
Inventory levels are monitored in real time. And all inventory management and control decisions can be made at any time based on current, accurate numbers. Because those numbers are all updated perpetually, after every purchase and every sale.