The Ebay Global Shipping Program is a simplified way to ship internationally. They take care of posting the item and clearing customs.
Customs charges tariffs for some things manufactured in a specific country. (A tariff is a tax placed on some items being imported into a country.)
Most items are made in China, and until recently, tariffs were limited or nonexistent. Going forward, because the Trump administration has decided to raise tariffs, there may be some tariffs.
Sometimes, particularly for less common expensive items, the country of manufacture may be in the USA, Japan, or a European country. Additionally, it’s likely that an international buyer will be in Japan or a European country. There may be tariffs between these countries.
To streamline the process, Ebay recommends that you specify the country of origin.
I have definitely failed to determine the country of manufacture, and have failed to specify the country of manufacture, but it could be important.
I recently sold a made-in-UK item to someone in the UK. I don’t recall setting that field in the listing’s features. If I had, the purchaser could benefit by paying a lower price. The seller would benefit by having Ebay display a lower price.