product vs period costs

Imagine a toy factory. Some money goes into the toys themselves — the plastic, the workers stamping out parts, the electricity for the molding machines. That money does not vanish when spent; it is now sitting inside finished toys on the shelf, waiting to be sold. Other money goes to things that have nothing to do with making a toy — the salaries in the sales office, the advertising, the CEO's salary. That money is simply gone for the period. The first kind is a product cost; the second kind is a period cost.

Precisely, product costs are the costs of making the product — for a manufacturer, direct materials, direct labor, and manufacturing overhead. They are 'inventoriable': they attach to the goods and sit on the balance sheet as inventory (an asset) until those goods are sold, and only then do they become an expense called cost of goods sold. Period costs are all other costs — selling and administrative expenses — and they are expensed immediately, in the period incurred, regardless of whether anything was sold. For example, if a factory spends 50,000 making 1,000 toys but sells only 600, then 30,000 (the cost of 600 toys) becomes expense and 20,000 stays on the balance sheet as inventory; meanwhile the 8,000 of advertising that month is fully expensed now.

This matters because the product/period split decides when a cost hits the income statement, and that timing can swing reported profit. A common confusion is to expense factory costs right away as if they were ordinary bills; in fact they are parked in inventory and released as expense only as units sell, which is why a factory can spend heavily this month yet report little expense if the goods are still unsold. The line is not 'important vs unimportant' — advertising is vital — but strictly 'part of making the product, or not.'