The way you display stock on the web site is an important factor in your relationship with your customers. You may want to show ‘out of stock’ messages to prevent disappointment when orders cannot be fulfilled in a timely manner. Likewise you may wish to show ‘low stock’ messages to encourage purchasing of attractive items. You will know how accurate your stock position is in your warehouse so the threshold that ‘out of stock’ and ‘low stock’ can be configured for the site. The default values are 0 for ‘out of stock’ and ‘low stock’ is not used.
It may be that the stock accuracy is wildly different between various categories of product in your warehouse. It may be that you mostly sell expensive electric pumps and the stock position is 100% accurate so zero is the correct threshold. Alongside the pumps you sell nuts and bolts stored in big bins and as they are also used internally the stock position is only correct to the nearest 100. In this case you can set the ‘out of stock’ threshold individually on this product and it will override the site wide setting.