Editorial: an article in a newspaper presenting the opinion of the editor(s) so it does not receive a byline because it represents the opinion of the newspaper.
Op-ed: (or “opposite editorial”) are articles devoted to commentary, feature articles, and opinions. Authors are not officially affiliated with the newspaper and can range from state legislators to local business owners and interested local citizens. Op-eds must be approved by the editorial page or opinion page editor and will also be cleared by a copy editor.
Letter to the Editor: usually written in direct response to an article, editorial, op-ed, or column that the paper has printed. They can also be a reaction to or notification of a newsworthy event. They are printed on the editorial page.
Column: A single article containing the author’s opinion
News Story: a news report of any length, usually presented in a straightforward style and without editorial comment. Most often written in the inverted pyramid style, with summary lead.
Featured Story: a story that is written to inform, but also to entertain. A feature article builds upon the interests of the audience and can be written more creatively than traditional inverted pyramid formatting. These stories focus on people and what they like to do, where they live, what they eat, what entertains them; the sky's the limit as long as it interests the audience.
News Analysis: More and more frequently, you’ll see newspapers such as The New York Times printing pieces that are not quite news articles, not quite editorials and not quite features. They go into more depth than a straight news article, described above, typically would, offering an analysis of events and how it might affect the surrounding area. Pieces like this require a great deal of knowledge about the event, the area in which it takes place and the people involved, and thus are usually written by more experienced reporters who specialize in covering certain areas or topics.
Press Release: written or recorded communication directed at members of the news media for the purpose of announcing something ostensibly newsworthy. Typically, they are sent to the assignment editors.
Scholarly v. Popular
A scholarly publication is one in which the content is written by experts in a particular field of study - generally for the purpose of sharing original research or analyzing others' findings. Scholarly work will thoroughly cite all source materials used and is usually subject to "peer review" prior to publication.
POP aim to inform a wide array of readers about issues of interest and are much more informal in tone and scope. Examples include general news, business and entertainment publications such as Time Magazine, Business Weekly, Vanity Fair.
Note, special interest publications which are not specifically written for an academic audience are also considered "popular" i.e., National Geographic, Scientific American, Psychology Today.