Slander is defamation by word of mouth; libel is defamation by publication (which includes all means of publication: circulating on paper, broadcasting, publishing on a website, etc).
The law tries to balance the equally important but often opposed demands for free speech and protection of reputation. Journalists, programme makers and broadcasters often need to say things about people that those people would prefer not to be said. The law allows you to report what is true or to comment on true facts.
If your report is untrue, or your comment based on untruth, the law protects the subject of your report or comment, if the words you have used expose him or her to the risk of being: