Censorship refers to the suppression of speech or information that is deemed objectionable by an authority. It can be conducted by governments, private institutions, or other controlling bodies. There are two main types of censorship: self-censorship, where an individual censors their own works, and authority censorship, where an outside body censors information. Authority censorship is used to control obscenity, protect children, promote or restrict political views, and prevent slander. Throughout history, censorship has been used during times of war to protect operational security and sensitive information. Different forms of censorship also exist such as political, religious, educational, and economic censorship which are used to limit expression and protect beliefs, children, and financial interests.