Inventory includes a small business's finished products, as well as the raw materials used to make the products, the machinery used to produce the products and the building in which the products are made. In other words, anything that goes into producing the items sold by your business is part of its inventory.
Stock
Stock is the finished product that is sold by the business. In some cases, stock is also raw materials, if the business also sells those products to its customers. For example, a car dealership's stock includes cars, but also can include tires, engine parts or other car accessories.