A journalist was someone who specialized in journalism: writing articles for a newspaper, magazine, or other periodical. Journalists who specialized in researching and disseminating information about events were called reporters.
In 2371, Captain Kathryn Janeway and Tom Paris encountered Latika, a young boy, whose father was a journalist. Latika proclaimed that he, too, was a journalist, writing for his school newspaper. (VOY: "Time and Again")
In 2372, Neelix became interested in journalism and tried to become a journalist. He even created his own program, A Briefing with Neelix, which was broadcast throughout the USS Voyager. He later investigated the rumors of a spy aboard Voyager, which turned out to be Michael Jonas, whom he later fought in engineering. During his investigation, Neelix was asked to withdraw the matter by Tuvok, who deemed it a matter of ship security, however Neelix did not concur, stating that "As a journalist, I have an ethical obligation to keep digging for the facts in this case." (VOY: "Investigations")
Jake Sisko was a journalist for the Federation News Service and reported on the Dominion occupation of Deep Space 9 and the First Battle of Chin'toka. (DS9: "Call to Arms", "A Time to Stand", "Rocks and Shoals", "Tears of the Prophets")