What is the difference between a reporter and a columnist at a news outlet?

No real difference. They basically play the same role and do the same work in a newsroom. Reporters work “beats.” Columnists stay in the newsroom and interview people by phone. Reporters produce “straight news” reports that aspire to be as fair and accurate as possible. Columnists produce pieces of opinion journalism that advance a particular point of view. Columnists are typically inexperienced journalists. None of the above.