Privacy is the ability of an individual or group to seclude themselves or information about themselves and thereby reveal themselves selectively. The boundaries and content of what is considered private differ among cultures and individuals, but share basic common themes. Privacy is sometimes related to anonymity, the wish to remain unnoticed or unidentified in the public realm. When something is private to a person, it usually means there is something within them that is considered inherently special or personally sensitive. The degree to which private information is exposed therefore depends on how the public will receive this information, which differs between places and over time. Privacy can be seen as an aspect of security — one in which trade-offs between the interests of one group and another can become particularly clear.

The right against unsanctioned invasion of privacy by the government, corporations or individuals is part of many countries' privacy laws]], and in some cases, constitutions. Almost all countries have laws which in some way limit privacy; an example of this would be law concerning taxation, which normally require the sharing of information about personal income or earnings. In some countries individual privacy may conflict with freedom of speech laws and some laws may require public disclosure of information which would be considered private in other countries and cultures.

Privacy may be voluntarily sacrificed, normally in exchange for perceived benefits and very often with specific dangers and losses, although this is a very strategic view of human relationships. Academics who are economists, evolutionary theorists, and research psychologists describe revealing privacy as a 'voluntary sacrifice', where sweepstakes or competitions are involved. In the business world, a person may give personal details (often for advertising purposes) in order to enter a gamble of winning a prize. Information which is voluntarily shared and is later stolen or misused can lead to identity theft.

Types of privacy

The term "privacy" means many things in different contexts. Different people, cultures, and nations have a wide variety of expectations about how much privacy a person is entitled to or what constitutes an invasion of privacy.

Physical

Physical privacy could be defined as preventing "intrusions into one's physical space or solitude" This would include such concerns as:

• preventing intimate acts or one's body from being seen by others for the purpose of [[modesty; apart from being dressed this can be achieved by walls, fences, privacy screens, cathedral glass, partitions between urinals, by being far away from others, on a bed by a bed sheet or a blanket, when changing clothes by a towel, etc.; to what extent these measures also prevent acts being heard varies
• video, as aptly named graphics, or intimate acts, behaviors or body part
• preventing unwelcome searching of one's personal possessions
• preventing unauthorized access to one's home or vehicle
• medical privacy, the right to make fundamental medical decisions without governmental coercion or third party review, most widely applied to questions of contraception