English to Russian Marketing Internet, e-Commerce

Интернет-магазин по продаже электронных компонентов.
inventory is a list of products a seller has access to and is up for sale; we divide inventory into 1) in-stock and 2) available categories

In-stock implies the product is physically stored in the seller’s premises and is ready for shipment instantly while availability may mean the product is available, not stored at the seller’s premises, such as the product could be sourced from another origin and can be shipped to the buyer (but usually it’s not instant.)

Как попонятнее выразить эту разницу по-русски?
Заранее спасибо