Censorship is the act of concealing societal vulgarities and obscenities from being purveyed onto the public-at-large and minors--those legally defined as such due to their age status and ability to be highly influenced.
Not all censorship is meant to be a public service. In some cases, such as the "great firewall" of China, censorship is a means to control the influence of outside politics from entering the country through media channels and the internet.
Additionally, censorship can also be employed by corporations in order to shape public perception. Legal means such as Non-Disclosure Agreements, information security classification(Top Secret, Secret, Classified, For Official Use Only), and contract stipulation can provide legal ramifications for violating terms of agreement that specify what can or cannot be said.