Doxxing is publishing and analysing others' personal information on the internet with a malicious intent that can reveal the person's real identity to make them victims of harassments and cyber attacks.
Doxxing is usually used in negative sense because it uses personal information of a person for illegal actions.
It uses publicly available databases from social media platforms (such as Facebook, Twitter etc.), via hacking and social media engineering to obtain personal information.
Recently, Meta (Facebook) has suggested Facebook and Instagram to make stricter doxxing rules, so that people's suspicious accounts can be suspended.