Canon

To understand canon and continuity, the overall series should be looked at as a set of stories written by many different people which "document" historical "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.

The situation can be compared to Greek and Roman mythology, or the stories of King Arthur and Christianity. The various Elder Scrolls tales are a group of separate but linked stories, and are told by many different authors over a period of time.

Canon and games
Things are a bit more complicated with the matter of The Elder Scrolls games. The overall scenario and documentation (cutscenes, manuals, strategy guides etc.) are proper canon. This, however, doesn't apply to "game mechanics" and stats. If the race or gender of a character is considered canon, then in-game events and characters that are 'triggered' when the non-canonical gender or alignment is selected are non-canon as well. Exceptions are made if a higher canon source, such as a book, state it as happening. In that case, the game is inconsistent to the canon and falls under the "game mechanic" logic.
 * Game mechanics are the "artistic license" properties of the game that separate any computer game from reality and serve to make one more playable and enjoyable; for example the Hero of Kvatch carrying 10 weapons simultaneously, fully and immediately recovering from wounds simply by waiting for an hour, bodies of defeated enemies disappearing etc., are things not realistically possible. Health, Magic points, and fatigue are also game mechanics.
 * Background or lore information given in the strategy guides such as biographies, stories, descriptions, etc. is proper canon. Stats, on the contrary, are considered game mechanics and include details such as weapon damage, speed, and character stats (strength, intelligence, endurance, health points etc.).
 * In mission and quest solving, canon is assumed to be the fullest and best outcome possible of each mission/quest available as given in the briefing or scenario. The Eternal Champion, the Nerevarine, the Hero of Kvatch, etc. never failed their quests. Although the player can avoid some optional quests, TESWiki assumes that those heroes managed to complete all the "available" feats.
 * Problems can arise with customizable options such as the race or gender or alignment of the main character, until Bethesda releases a definite answer on this.
 * TESWiki articles assume that the player picks the good choice for all scenarios; therefore, even the secondary choices and events pertaining to the evil choice or triggered by relevant choices, are considered non-canon.
 * On the other hand, ambiguity is maintained when it comes to alternative choices and solutions to puzzles with the same outcome. For example in The Elder Scrolls IV: Oblivion, which Daedric artifact you give to Martin in the main quest is up to the player; and none of them can be taken for sure to be the 'true' one.