Privacy is the freedom from unauthorized intrusion: state of being let alone and able to keep certain especially personal matters to oneself. The right not to be subjected to unsanctioned invasions of privacy by the government, corporations or individuals.

Privacy of the person encompasses the right to keep body functions and body characteristics (such as genetic codes and biometrics) private;

Privacy of behavior and action includes sensitive issues such as sexual preferences and habits, political activities and religious practices;

Privacy of communication aims to avoid the interception of communications, including mail interception, the use of bugs, directional microphones, telephone or wireless communication interception or recording and access to email messages;

Privacy of data and image includes concerns about making sure that individuals’ data is not automatically available to other individuals and organisations and that people can “exercise a substantial degree of control over that data and its use”;

Privacy of thoughts and feelings refers to the right not to share their thoughts or feelings or to have those thoughts or feelings revealed. Individuals should have the right to think whatever they like;

Privacy of location and space means individuals have the right to move about in public or semi-public space without being identified, tracked or monitored;

Privacy of association (including group privacy) is concerned with people’s right to associate with whomever they wish, without being monitored.

There is wide spectrum of how privacy is violated in our digital world even without general public awareness (privacy invasion, improper acquisition, use, storage). Privacy should be protected adopting a regulatory and/or technical approach.

“You have to fight for your privacy or you will lose it“ (Eric Schmidt, Google/Alphabet, 2013)

Check this rich wikipedia definition for further information.