Star Wars Canon IS The Expanded Universe Is No longer Considered Canon And IS Re-Termed As The "Legends"
As of April 25, 2014, the only previously published materials that are considered canonare the six Star Wars films and the Star Wars: The Clone Wars television series and film, while the Expanded Universe is no longer considered canon and was re-termed as the "Legends" brand.
"'Gospel,' or canon as we refer to it, includes the screenplays, the films, the radio dramas and the novelizations. These works spin out of George Lucas' original stories, the rest are written by other writers. However, between us, we've read everything, and much of it is taken into account in the overall continuity. The entire catalog of published works comprises a vast history—with many off-shoots, variations and tangents—like any other well-developed mythology."
To understand canon and continuity, the overall Star Wars saga should be looked at as a set of stories written by many different people which "document" past "events." Although some stories are more reliable than others, they all are looked upon as part of the overall "history." It should also be remembered that all of these stories are simply that—stories. There are numerous errors that inevitably arise between the stories simply because different authors have their own ways of telling the story and may not have the time and resources to perfectly align the details. This site deals with non-canon material by putting red text notification above the non-canon items.
The situation can be compared to Greek and Roman mythology, or the stories of King Arthur. The various Star Wars tales are a group of separate but linked stories, and are told by many different authors over a period of time.