According to Wikipedia:
Gross domestic product (GDP) is a monetary measure of the market value of all the final goods and services produced in a period of time, often annually or quarterly. Nominal GDP estimates are commonly used to determine the economic performance of a whole country or region, and to make international comparisons.
But what if a country has a product which is massively or at least moderately produced and consumed only locally, either for tradition or any other reason. And the exports of this product are non existent or at best minimum. In the case the exports are non existent, the international market value of this product would be zero, wouldnt be? Or does the national market value counts in this case? Also, if the international market exists but it's minimum, and most of the production can only be consumed localy, does all those unsalable products value contribute to the GDP value?