More precisely, it is a documentary contaminated with fictional elements, in real time, filmed when the events take place, and in which someone – the character – plays his own role in real life. A film genre in expansion, it is adopted by a number of experimental filmmakers.
The new term docufiction appeared at the beginning of the 21st century. It is now commonly used in several languages and widely accepted for classification by international film festivals. Either in cinema or television, docufiction is, anyway, a film genre in full development during the first decade of this century.
In contrast, docudrama is usually a fictional and dramatized recreation of factual events in form of a documentary, at a time subsequent to the "real" events it portrays. A docudrama is often confused with docufiction when drama is considered interchangeable with fiction (both words meaning the same). Typically however, "docudrama" refers specifically to telefilms or other television media recreations that dramatize certain events often with actors.
A mockumentary (etymology: mock documentary) is also a film or television show in which fictitious events are presented in documentary format, sometimes a recreation of factual events after they took place or a comment on current events, typically satirical, comedic or even dramatic (see genres: drama versus comedy and tragedy). Portraying events at an ulterior time and basically using fictional narrative such as docudrama, it should not be confused with docufiction as well.
In the domain of visual anthropology, the innovating role of Jean Rouch allows one to consider him as the father of a subgenre called ethnofiction. This term means: ethnographic documentary film with natives who play fictional roles. Making them play a role about themselves will help portray reality, which will be reinforced with imagery. A non ethnographic documentary with fictional elements uses the same method and, for the same reasons, may be called docufiction.
Filmic depictions of ethnic groups became a current practice since Flaherty shot Nanook of the North in 1922 (the first feature-length documentary in film history, a docudrama) and since, under its influence, Jean Rouch pioneered ethnofiction with Moi un noir (1958, foreshadowing the French New Wave) and coined this term as a new genre in visual anthropology. Subsequently, the concept of ethnofiction (ethnography+fiction) would exceed scientific practice and, by analogy, give rise to a wider designation (docufiction: documentary+fiction) in which it would be ranged as subgenre. Such designation would then be used to classify films that early emerged in several countries, directly under Flaherty’s influence or indirectly by occasional resemblance, in both cases with no correlation and with significant differences in form and contents. On one hand hybridity became one of the criteria that joined documentary and fiction in a single concept. On the other hand, persons playing their own roles in real life and in real time is another that gave basement to it. Both these requirements are closely associated with two other in the practice of docufiction: 1. ethics and aesthetics, i.e., fidelity to truth and reality, 2. signifiers and connotations, i.e., forms of expression picturing facts in an illustrative or allusive way, unveiling facets of human life.
Modernity is the motor that made docufition cross a new frontier and find land to grow, a large territory governed by ambiguous figures who face each other. Sometimes they empathize. Others they go angry. They exceed themselves in extreme situations.
Things went wrong for the first time with a sad story: Children of Hiroshima (1952), survivals of a colossal tragedy, a story of revenge starred by The Great Artiste and by the Necessary Evil. A story of tremendous explosions which imploded in cathartic effects, devastation and suffering in pictures of great beauty, in black and white. Face to it, one must submit to an extreme requirement: such things must not be done.
In same style and much lower scale, new attempts have been made to cause similar effects. In different style and in diverse scales, others would be made to arise less pathos and more acute understanding of modern realities. How far can they go? How far author vanities injure spectators? Will this perverse fashion have a future? Films like these have been few. Will be many those which follow? Will they fit to modern definitions?  (See: Postmodernist film)
Illustration and allusion ("recording" and "interpretation" ) are the poles of two different forms of mirroring reality, either in film or any other art. Illustration techniques are objective and implicate a concern of fidelity to what they represent, to the “representant”, the signifier. Allusion represents subjective matter.
Robert Flaherty would illustrate the realities he pictured with appealing aesthetics, realities that touched naïve audiences thirsty of alluring landscapes: exotic natives, beautiful and noble savages from dream countries faraway. He showed them with strong images, conceived to please large audiences and greedy producers. As well seduced by such charms, Jean Rouch, a scientist before everything else, ventured to go further in extreme attempts. Using neutral lenses and a quite different sense of poetry, he went shooting blacks in mysterious countries of Africa with the noble intent of discovering who they are and what they mean. He submitted to confrontation in both fronts: reducing aesthetics to images with no pretention and ethics to strict principles, indispensable to bring up truth.
The stories these adventurers tell about such encounters are cryptic and highlight an uncomfortable paradox that haunts them all in different ways. It affects audiences someway.
From different countries, others try the same. For strong reasons, a few dare to go beyond the limits they should keep, turning documentary into irreducible fiction, into fantasy with no return: The 1001 Nights , Horse Money e.g., in radical approaches but different moods (reveries, dramas, country paradigms). Others, in matching moods and similar attempts, afraid to veer, set foot on redlines without scalding, using subtle tricks, ingredients with less burning effects: Taxi, Drifts e.g.(autobiographies, city portraits, no budget films, metafilms, docu-comedies in extreme). Both tendencies will survive. Mutant realities will make them vary.
^Note, however, that Flaherty's earlier film, Nanook of the North from 1922, incorporates many docufiction elements, including the "casting" of locals into fictitious "roles" and family relationships, as well as anachronistic hunting scenes.