What is area code when someone is text from different country?

The meaning of your question is unclear.

If you are trying to send a text to someone who has the same area code, but that person is currently physically located in a different country, you can send the text the same way you normally do. If the person has roaming service turned on, they will receive your text; otherwise, they will receive it when they get back.

If you are trying to send a text to someone who is from a different country, but their cell phone happens to have the same area code in their country that your cell phone has in your country, you can send them a text using the full international number, beginning with the plus symbol and the country code (examples: UK = +44, France = +33, Australia = +61).