Can I put a placeholder with a description or example in text fields?

I am a beginner at UX writing so I can use the wrong terminology - sorry about that. I am currently working on admin panel and have a lot of text fields for data entry about banks, users and so on.

I wanna find out what exactly kind of text should replace 'placeholder' text.

For banks, for example, can I invent a name and use it instead of 'placeholder' or should I just leave it empty? Or for users, can I invent a user (name, fake email and so on) and use it in text fields? For example: