This, "A Nightmare", is one of Georges Méliès's earliest films. It's one of his first films to feature a formula he would return to for many of his subsequent productions, from "The Bewitched Inn" (L'Auberge ensorcelée (1897)) to "The Black Imp" (Le Diable noir (1905)). The setup is simply a man trying to sleep despite nightmares or bizarre happenings to his surroundings (often, furniture and such moving, disappearing and appearing). These films provided Méliès with plenty of opportunities for his trick effects--mostly stop-substitutions (or substitution-splicing).
"A Terrible Night" (Une Nuit terrible (1896), an earlier film by Méliès, is the earliest available example of this genre, but that film didn't contain any filmic trick effects. Another previous film of his, "The Vanishing Lady" (1896), had stop-substitution tricks presented within a magic trick. "A Nightmare" features a different device to present its magic--that is, dreams. In later films, Méliès would also introduce fairies, malevolent wizards and other devices (i.e. science fiction and aliens in the case of the more elaborate "A Trip to the Moon") to present his trick effects, which allowed them to be at least within something resembling a narrative.
The most noteworthy of the dream images, I think, is the moon with a face, which bites the protagonist's hand. Méliès would again use the moon in such films as "The Astronomer's Dream" (1898) and "A Trip to the Moon" (1902). Additionally, this film contains five backdrop changes, all accomplished through editing, as with the character appearances and disappearances. The film was shot in the open air, as indicated by the shadows. The early history of film is scattered with knockoffs of Méliès's films; for example, one of the more popular early films remaining today, "Dream of a Rarebit Fiend" (1906) was clearly a product of this genre "A Nightmare" helped initiate.
