I think of inventory as a company's goods on hand, which is often a significant current asset. Inventory serves as a buffer between a company's sales of goods and its production or purchase of goods. Companies strive to find the proper amount of inventory to avoid lost sales, disruptions in production, high holding costs, etc.
Manufacturers usually have the following categories of inventories: raw materials, work-in-process, finished goods, and manufacturing supplies. The amounts of these categories are usually listed in the notes to its balance sheet.
A company's cost of inventory is related to the company's cost of goods sold that is reported on the company's income statement.
Since the costs of the items purchased or produced are likely to likely to change, companies must elect a cost flow assumption for valuing its inventory and its cost of goods sold. In the U.S. the common cost flow assumptions are FIFO, LIFO, and average.
Sometimes a company's inventory of goods is referred to as its stock of goods, which is held in its stockroom or warehouse.