When you enter a new product to your Startershop, you will be asked to enter a stock level i.e. tell the system how many of these products you have available to sell. This means that if a customer tries to order an item which is out of stock, the system will prevent the order from going through and inform your customer of the situation.
When products run out of stock they are not removed from the shop, as this would confuse Search Engines, but are marked as out of stock and customers are prvented from purchasing them.
Of course if you have a limitless supply of a given product, simply enter a high stock level so that, from the system’s perspective, you never run out of stock.