100% is a route that exists on many versions of the game, with the most popular being the 100% route for PC (2013). The reason this particular version is preferred is because it allows the use of Chocobo World and in turn the Item Glitching it abuses. This reduces the time to acquire items and makes the run RTA viable at about 12 hours.
The route for 2013 PC was defined by XeroKynos as:
"Defeat all bosses, get all GFs, finish all side quests, have 1 of each item, have all cards (in possession), all characters have their ultimate weapon, all characters have learned all of their limit breaks, all junctionable GFs have learned all of their abilities (no abilities that can't be taught again were forgotten), all tutorial entries are known, enter all item shops and 12 Timber Maniacs magazines have been obtained."
More detailed rules and a checklist for the speedrun can be found here.