title: REST API Magneto: difference between product id and item id
body: <p>According to documentation <a href="http://devdocs.magento.com/guides/m1x/api/rest/Resources/inventory.html#RESTAPI-Resource-StockItems-HTTPMethod-PUT-stockitems--id" rel="nofollow">REST API: Stock Items</a>
  HTTP Method: PUT /stockitems has options <strong>product_id</strong> and <strong>item_id</strong>.
  I'm interested which is the difference between them?</p>