Privacy
Privacy is the ability to choose what information or personal data is hidden and who it's hidden from.
Privacy laws in many countries give the right not to be unfairly subjected to invasions of privacy.
The Universal Declaration of Human Rights says that privacy is a human right.
Importance
Everyone wants to keep things about them private.
Some people want to keep their religion, sexual orientation, and opinions private so that they don't get in trouble with their government, the people they know, or both.
Internet privacy
Many things on the internet are tracked and sometimes sold by different groups of people.
For example:
Your internet provider can see the names of the websites you go to (for example: Wikipedia), if the website uses HTTPS. If a website uses HTTP your internet provider can see the exact page you're in (for example: Privacy page on Wikipedia) and things you write in that website (Like your password). This is why HTTPS is considered by web browsers as safe but HTTP is not.
Google tracks and stores data created by the Google searches you make, the emails sent from and to Gmail addresses, on all websites you visit that use Google Analytics, and more.
TikTok collects and shares location data, sees private messages, sells your personal information to others, and more.
The senders of an email can track the time you open an email using pictures that sometimes can't even be seen.
Notes
References
Human rights