Short answers, pulled from the story.
Censorship is the suppression of speech, public communication, or other information considered objectionable, harmful, sensitive, or inconvenient. It can be conducted by governments and by private institutions, and when an author or creator suppresses their own work it is called self-censorship.
In 1766, Sweden became the first country to abolish censorship by law.
The main types include moral censorship of obscene material, military censorship of intelligence and tactics, political censorship that withholds information from citizens, religious censorship of material a faith finds objectionable, and corporate censorship by editors protecting a business. Other forms include self-censorship, financial censorship, soft censorship, reverse censorship, and economic induced censorship.
During the Allied occupation of Japan, the CCD was active from 1945 to 1949 and opened 200 million pieces of mail and 136 million telegrams while tapping telephones 800,000 times. No criticism of the occupying forces was allowed, including the dropping of the atomic bomb and crimes by U.S. soldiers, and those caught were placed on a blacklist called the watchlist.
China uses sophisticated mechanisms known as the Golden Shield Project to monitor the Internet, and search engines such as Baidu remove politically sensitive results. A 2013 study led by Harvard professor Gary King found that social media posts mentioning collective action were far more likely to be deleted than posts merely supporting or criticizing the government.
In 399 BC, Socrates went on trial in Athens and was found guilty of corrupting the minds of the youth and of impiety, defined as not believing in the gods of the state, and he was sentenced to death. The conviction is recorded by Plato.