They ask you to log in with your Facebook credentials, effectively stealing your password.
It was him.
Can people tell that I've seen their Facebook profile? ... No, Facebook doesn't tell people that you've seen their profile. Third- Who views your Facebook profile | Facebook Help Center facebook profile viewer in facebook
If you’ve ever been curious about who’s stalking your Facebook page—an ex, a secret admirer, or a nosy coworker—you’ve probably searched for a directly inside Facebook or on Google. They ask you to log in with your