The Dragon Elders are a group of old Dragons who live in the Dragon Dojo and govern the Dragon Realms. In the Advance spin-off series, "Dragon Elder" is a collective term that refers to all older Dragons. The Dragon Elders are mentioned but do not appear within the actual series until Spyro: A Hero's Tail.
A yellow colored dragon (appearance shared alike with Titan) appeared in Spyro 2: Season of Flame, but has no specific name given other than "Elder".
A dragon sensei is specifically the same thing as a Dragon Elder, however, the senseis are more targeted towards teaching dragons how to fight and concentrate rather than directly teaching focus. Senseis otherwise are the same thing.