Star Wars saga

The Star Wars saga, also referred to as the Skywalker saga, is the primary Star Wars movies, which began in 1977 with Star Wars: Episode IV A New Hope and is slated to end in 2019 with the release of Star Wars: Episode IX. It presently consists of a set of trilogies: the original trilogy, the prequel trilogy, and the sequel trilogy.

The Star Wars saga differs from other Star Wars theatrical film series, including The Star Wars Holiday Special, Caravan of Courage: An Ewok Adventure, Ewoks: The Battle for Endor, Star Wars: The Clone Wars, Star Wars Anthology Series, an upcoming Untitled Star Wars film series, an the forthcoming Untitled Star Wars trilogy.

Films
In story order:
 * Prequel Trilogy:
 * Star Wars: Episode I The Phantom Menace
 * Star Wars: Episode II Attack of the Clones
 * Star Wars: Episode III Revenge of the Sith
 * Original Trilogy
 * Star Wars: Episode IV A New Hope
 * Star Wars: Episode V The Empire Strikes Back
 * Star Wars: Episode VI Return of the Jedi
 * Sequel Trilogy
 * Star Wars: Episode VII The Force Awakens
 * Star Wars: Episode VIII The Last Jedi
 * Star Wars: Episode IX

Episode titles
The-as-of-present eight released Skywalker Saga begin their designation with "Episode" followed by their chronological order displayed as a roman numeral.

Star Wars: Episode IV A New Hope, was originally released simply as Star Wars, as there was not yet clarity or green light for a sequel. Beginning with its April 10, 1981 re-release, (11 months after The Empire Strikes Back) it was renamed to Star Wars: Episode IV A New Hope.

Canon
Prior to the 2014 Disney Canon reboot ("eliminating" most of the Extended Universe) the then six Saga Films (Episodes I-VI) were the highest level of a 6-tier canon system, known as G-Canon (or George Lucas Canon).

In defining the reboot, Disney streamlined everything into two categories: Canon and Legends. Almost everything that was not a Saga Film became Legends; three exceptions included: The Clone Wars TV Series, its introductory movie, and Darth Maul—Son of Dathomir (a Dark Horse, 4-issue comic book mini-series based on unproduced The Clone Wars Season 7 scripts).

Going forward, most (if not all) Disney-created Star Wars content will be canon, especially the Saga's concluding trilogy of Episodes VII-IX.

Opening crawls
All of the Saga Films begin with the blue text "A long time ago in a galaxy far, far away…" card which is then immediately followed-by the Star Wars logo and the slanted, yellow-text-on-starfield summaries of immediately preceding off-screen action. While the typefaces vary slightly, these all follow the same overall general format.

These crawls were inspired by the Flash Gordon serials of George Lucas' childhoodundefined. At present, the Anthology and TV Movies do not contain these, nor are future non-Saga media expected to.

The Skywalker lineage
While possibly not first intended as such, the movies, at minimum, evolved into tracing Clan Skywalker through all 9 arcs:

The Original Trilogy (Real-World: 1977 - 1983; In-Universe: 0 BBY - 4 ABY) focuses on protagonist Luke Skywalker, his unknown-to-him sister Princess Leia, and the reveal and redemption of their father, antagonist and former Jedi-turned-Sith Lord, Darth Vader/Anakin Skywalker.

The Prequel Trilogy (Real-World: 1999 - 2005; In-Universe 32 BBY - 19 BBY) focuses on protagonist Anakin Skywalker as he matures from 9-year-old Tatooine slave child to Padawan to Clone Wars General and galaxy-defending Jedi Knight. His mother, Shmi Skywalker, features significantly in Episode I, also as a slave, with a return cameo in Episode II, in-which her later-and-surprise marriage provides Anakin with a previously unknown step-father and step-brother (who "retro-actively" appears in Episode IV as Luke's uncle).

The Sequel Trilogy (Real-World: 2015 - 2019; in-universe: 34 ABY - ?? ABY) focuses on the next generation, with special attention to antagonist Kylo Ren/Ben Solo, the bloodline and grandson of Anakin Skywalker, through his mother, General Leia Organa, initially Jedi-trained by his uncle, Luke Skywalker. Kylo survives Episode VIII and should be seen in the conclusion of Episode IX.

Monomyth
The trilogies follow Joseph Campbell's concept of Monomyth, or, "The Hero's Journey" Cycle, as Lucas studied Campbell's The Hero with a Thousand Faces and more while composing his universe.

Timeline boundaries (32 BBY - 34 ABY)
This characteristic is the most likely to change in some regards. The Disney 2014 Canon Reboot initially reset the entirety of Canon between 32 BBY and 4 ABY (36 years, approximately the same as G-Canon) making The Phantom Menace and Return of the Jedi the effective bookends of Canon. This practice continued in 2015's The Force Awakens, moving the current, final bookend to 34 ABY (2017's The Last Jedi takes place just moments after, also in 34 ABY), 66 years later.

Of note, the other Canon-but-not-Saga Reboot survivors, The Clone Wars Movie, TV Show and Darth Maul—Son of Dathomir, take place between 22 BBY and 19 BBY, clearly within the original reboot's timeline.

Presently, the slowly expanding Canon media closely adheres to these bounds (the 5-Part arc of the Star Wars comic "Yoda's Secret War" (Issues 26-30) taking place less than a year before The Phantom Menace). As all Saga Films are Canon, this practice of Timeline Boundaries may continue, but with many announced-but-unnamed film deals taking place, future Canon-but-not-Saga films are expected to take place outside this timeline.

One feature of this characteristic that seems now immutable is the importance and prominence of the Saga Timeline and its focal point: Star Wars events are measured in BBY/ABY, Before/After the Battle of Yavin (IV), the climactic finish of the Death Star I in A New Hope. At present, the apparent completed Saga will be almost evenly distributed before and after this event. Old, popular Legends properties, such as Knights of The Old Republic, blantantly use the Battle of Yavin and either subtly-or-blatantly use the Saga as their reference point for measuring time (and possibly softer-to-quantify concepts such as Jedi-Sith relations). It is reasonable and expected that future, far-reaching Canon properties will have to follow this trend.

"Plans"
George Lucas has changed the "planned" number of Saga Films from interview-to-interview over the years (with potentially as many as twelve as far back as 1978). After Disney acquired Lucasfilm in 2012, their "announced" Saga Films presently rests at a total of 9, as they develop more television shows, web series, Anthology Films, other films and trilogies.