Censorship is the act of preventing specifically-defined ideals, concepts, images, or messages from being available to a given population. For example, the "great firewall" that is run by the Chinese government, 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.
The prominence of censorship can be always debated depending on the position, viewpoint, and motivation of the parties involved in the dispute.