Assembly SKUs are SKUs that are built using components that you can also sell individually. A perfect example of this would be a desktop computer if you also sell memory, hard drives, and power supplies.
The final assembled SKU can have inventory, but as long as the components are still in stock, the system will allow customers to continue to purchase the finished products. Once any of the needed component pieces are not in stock to the needed quantity (example: having less than 4 count of RAM if you need 4 sticks of RAM per computer.), then the assembled SKU becomes out of stock and is affected by its backorder option.
You can learn more about Assembly SKUs here.
You can toggle how you want your Assembly SKUs to be treated from customers on the storefront; some merchants may only want customers to purchase fully assembled SKUs, and not allow them to add the item to the cart if only the components are available. This could be due to long build times, only building the Assembly SKU at specific times, etc. This only affects front-end orders; MOTO orders can still add the Assembly SKU to orders even if the SKU is out of stock as usual.
This setting change requires Pulse Commerce Support's assistance. If you need to make this change for your site, please contact our Support team.