For questions about the trilogy of movies or books, 'The Fellowship of the Ring', 'The Two Towers' and 'The Return of the King'. Always use in conjunction with the [tolkiens-legendarium] tag and, for movie questions, the relevant movie tag, e.g. [fellowship-of-the-ring].
The story began as a sequel to Tolkien's earlier, less complex children's fantasy novel The Hobbit (1937), but eventually developed into a much larger work.
Although known to most readers as a trilogy, the work was initially intended by Tolkien to be one volume of a two-volume set, with the other being The Silmarillion. However, when Tolkien submitted the first volume entitled The Lord of the Rings to his publisher, it was decided for economic reasons to publish the work as three separate volumes, each consisting of two books, over the course of a year in 1954–55, creating the now familiar Lord of the Rings trilogy. The three volumes were entitled The Fellowship of the Ring, The Two Towers, and The Return of the King. Structurally, the volumes are divided internally into six books, two per volume; with several appendices of background material, much abbreviated from Tolkien's originals, included at the end of the third volume. The Lord of the Rings has since been reprinted numerous times and translated into many languages, becoming one of the most popular and influential works in the field of 20th-century fantasy literature and the subject of several films.
The title of the novel refers to the story's main antagonist, the Dark Lord Sauron, who had in an earlier age created the One Ring to rule the other Rings of Power as the ultimate weapon in his campaign to conquer and rule all of Middle-earth. From quiet beginnings in the Shire, a Hobbit land not unlike the English countryside, the story ranges across north-west Middle-earth, following the course of the War of the Ring through the eyes of its characters, notably the Hobbits Frodo Baggins, Samwise "Sam" Gamgee, Meriadoc "Merry" Brandybuck and Peregrin "Pippin" Took, but also the Hobbits' chief allies and travelling companions: Aragorn, a Human Ranger, Boromir, a Human soldier, Gimli, a Dwarf warrior, Legolas, an Elven prince, and Gandalf, a Wizard.
Tolkien's work has been the subject of extensive analysis of its themes and origins. Although a major work in itself, the story was only the last movement of a larger epic Tolkien had worked on since 1917, in a process he described as mythopoeia. Influences on this earlier work, and on the story of The Lord of the Rings, include philology, mythology, religion and the author's distaste for the effects of industrialization, as well as earlier fantasy works and Tolkien's experiences in World War I. The Lord of the Rings in its turn is considered to have had a great effect on modern fantasy; the impact of Tolkien's works is such that the use of the words "Tolkienian" and "Tolkienesque" has been recorded in the Oxford English Dictionary.
The enduring popularity of The Lord of the Rings has led to numerous references in popular culture, the founding of many societies by fans of Tolkien's works, and the publication of many books about Tolkien and his works. The Lord of the Rings has inspired, and continues to inspire, artwork, music, films and television, video games, and subsequent literature. Award-winning adaptations of The Lord of the Rings have been made for radio, theatre, and film.
The novel was adapted for film by director Peter Jackson. The three films (titled The Lord of the Rings: The Fellowship of the Ring (2001), The Lord of the Rings: The Two Towers (2002) and The Lord of the Rings: The Return of the King (2003)) have each grossed approximately a billion dollars and have been seen by an estimated 2 billion people.
From: The Lord Of The Rings on wikipedia
Questions with this tag should also always be tagged with the tolkiens-legendarium tag, which covers the whole franchise of works in Tolkien's universe, such as The Silmarillion and The Hobbit.