A WMS (Warehouse Management System) is the software that knows, at any moment, how much of which product sits in which location of the warehouse. Where an ERP knows the total quantity in stock, the WMS knows the aisle, the rack and the shelf, and tells employees the shortest route for receiving, put-away, picking and shipping.
What a WMS actually does
At receiving, it logs pallets by barcode scan and suggests a location. At picking, it groups picks by zone and wave to reduce walking. At shipping, it validates that the right SKU goes in the right box. It applies rotation rules (FIFO, LIFO, expiry date) and flags inventory discrepancies as they happen rather than at the annual count.
WMS and ERP
The two complement each other: the ERP manages the order and the invoice, the WMS manages the physical moves. Many ERPs include a basic warehouse module, enough for a small stock; once the warehouse holds thousands of references or several pickers, a dedicated WMS pays for itself.
Custom or standard
A standard WMS suits a classic distribution warehouse. Quebec distributors and manufacturers with particular rules (lots, consigned parts, assembled kits, dynamic slotting) often get a better result from a custom WMS plugged into their existing ERP. The Distribution MA project, where shipping errors dropped by 75%, illustrates that gain.