First and most important editorial photography is for the purpose of publication (magazines, newspapers, etc.). Editorial images are usually meant to accompany text and can cover a wide range of subjects. Editorials are used to illustrate a story, article, text or an idea within the context of a magazine or to embellish a certain theme visually. It can be in any genre: photojournalism, fashion, portrait, sports, landscape, etc. Editorial photographs may also tell a story by themselves without a written word or may be accompanied by a short topic or title of an intended story.
This is what happens in fashion field. Fashion editorials often feature as full page photographs on a particular theme or concept, designer, model or other single topic. Usually they are fashion images that tell a story or suggest that there is a back story to the photo. They may also serve as photo-essay to illustrate unwritten story. In this case creative editorial stories are born and they may take several spreadsheets in magazine.
Fashion editorials are not about a ton of clothes. These editorials are more about the mood and the situation the garments would be worn in. In editorial photography clothes can become an illustrative mean to tell a fashion story or at least make it look like fashion story but it is never limited to fashion.
Editorial photography goes along with edgy concept and it does not tell a story in a traditional sense.
There may also be no story at all. A mixture of fashion,lifestyle and location usually creates viewers emotion and gives an impression of a story behind. It makes viewer to think and to take another look at it. Usually edginess can be achieved by untraditional lighting, intense model poses, extreme makeup and hair or certain shooting location. Sometimes these strong visuals are what unite the series of shots. Editorials generally have a different wardrobe per page/spread and it also may have the whole wardrobe of similar look, for example, red.
Not every editorial has to be outdoors, on location or have a lot of props. Some can be as simple as a grey backdrop. Shooting a model in front of a seamless gray backdrop can be very editorial depending on the lighting, clothes, make-up, etc. Magazines also include beauty editorials that focus on makeup, hair and/or accessories. Usually fashion editorials are highly styled; they give a lot of creative freedom that is controlled by a photographer.
On the other hand, editorial defines usage not style. Editorial fashion came about when people of advertising world decided to sell the product in a less straightforward way. In this way focus falls less on the actual product but more on the telling of a story as a means to sell the item. The fact is that editorial images are not advertisements. Editorials come along with credits line and sell story. Advertising images are always anonymous and created to sell a particular product.
Commonly editorials are assigned by editors who dictate the story, idea or theme of the magazine for the particular issue. Editorial art directors like smart, sharp images with straight lines and clean composition. The difference with shooting for magazines is that the images often take up the entire page and need bleed room. It simply needs giving extra room along the sides. By the way, magazine covers are also editorials.
Generally speaking, editorial fashion photography has a very broad meaning and there is no absolute definition of it. Editorials may illustrate one printed word or may give the reader a perspective of what the whole concept is about. Editorial photography gives artists a lot of freedom in creativity and interpretation to show what words cannot communicate.