What do you mean by source language and target language?

And the source language of the target language.

Bilingual control

Example:

1.

What are some confusing things in your target language?

What's confusing about your target language?

article.yeeyan.org

2.

Seriously, stop learning so many target languages!

Seriously, don't be busy learning foreign languages!

article.yeeyan.org

3.

First of all, the first choice is to find a translator whose mother tongue is the same as the target language, and what will the final document look like.

First of all, priority should be given to translators whose mother tongue is the target language (that is, the language of the final document).