Alien = the technical term you see on immigration documents and in the law. Foreigner = the general term used in normal speech. Actually, it's a bad idea to use either of these words in conversation.

Thanks for your response, will in my country we do the same yours, but we don't say foreigner instead that we called the people by their country's name for example ( He is Japanese or from Japan not a foreigner )

In Japan, people from foreign countries are called 'foreigners' means '外国人’ . 'Alien ' is usually used in official documents, sounds bad for me. What about in your country?

Sometimes I think that "alien" has come to mean "extraterrestrial". Nationality is sometimes more of an attitude.