Some stores sell many products that are physically the same item. A print-on-demand store might list two hundred designs, but every "Small black hoodie" order — whatever the design — ships from the same stack of blank small black hoodies. If each design tracked its own stock, the numbers would drift apart from reality and you could oversell the blanks. An inventory group solves this: one shared stock pool that many products and variants draw from.
How it works
Create an inventory group for the physical item — for example "Black Hoodie S" with its own SKU — and set its stock per location. Then, on each product or variant that ships as that item, link it to the group from the product form's inventory section. From that point the linked products stop tracking their own stock: availability, reservations, and deductions all happen on the group.
When any linked product sells, the order reserves stock on the group; when it ships, the group's quantity drops and the movement is recorded in the group's stock history with the order as its reference. Because there is only one number, selling design A and design B at the same time can never oversell the blanks — they are both drawing from the same pool.
What the group shows you
The group page shows the pool the way the warehouse sees it: quantity, reserved, and available per location; how many products and variants are linked. The low stock alert fires on the pool, not per design — one alert when the blanks run low, instead of two hundred.
When not to use one
If a product is its own physical item with its own stock, plain per-product inventory tracking is simpler — link a product to a group only when its stock is genuinely shared with something else.