Xyz Tuner Monsters are simply Xyz Monsters that are also listed as Tuners, similar to Toon Monsters, Union Monsters or other special variants of Effect Monsters. Unlike Synchro Monsters or Fusion Monsters, Xyz Monsters were largely unable to be treated as Tuners through cards such as " " or " " due to having Ranks instead of Levels (though cards such as " " do make it possible). Regardless, these are still simply both Xyz Monsters and Tuner Monsters with all the rules and conditions that normally apply to both respective types of Monsters.
Due to having Ranks, all Xyz Tuner Monsters possess the same sentence in their lore: Cannot be used as a Synchro Material Monster while it is not treated as having a Level (with the exception of Number 60: Stream Synchron). By the same token, all Xyz Tuner Monsters also possess some effect that allows them to be treated as having a Level, in order to be used for Synchro Summons.