Fact checking is the act of checking factual assertions in non-fictional text in order to determine the veracity and correctness of the factual statements in the text.
Nonfiction or non-fiction is content whose creator, in good faith, assumes responsibility for the truth or accuracy of the events, people, and/or information presented.
Fact-checking the candidates' debate claims by Fox News
This may be done either before or after the text has been published or otherwise disseminated.
PolitiFact's Guide to Fact-checking by PolitiFact
Ante hoc fact-checking aims to remove errors and allow text to proceed to dissemination.
Post hoc fact-checking is most often followed by a written report of inaccuracies, sometimes with a visual metric from the checking organization.
Several organizations are devoted to post hoc fact-checking, such as FactCheck.org and PolitiFact.
PolitiFact.com is a project operated by the Tampa Bay Times, in which reporters and editors from the Times and affiliated media fact check statements by members of Congress, the White House, lobbyists, and interest groups.
FactCheck.org is a nonprofit website that describes itself as a non-partisan "consumer advocate for voters that aims to reduce the level of deception and confusion in U.S. politics".