Whis is the attendant and teacher of the 7th universe's God of Destruction, Beerus. His sister Vados is the attendant to Champa of the 6th universe.
Beerus learned of the Saiyans and fought Goku on Earth who transformed into a Super Saiyan God. Thanks to Bulma and the food and treats she supplies Whis, he took in Vegeta as a pupil. Of course when Goku learned this he asked and was accepted as a pupil as well. Whis began their training to master their God ki as well as trying to teach them to react without thinking.
Powers and Abilities
While the exact upper limits of Whis power have yet to be demonstrated he is still by far one of the most powerful beings in the DB Universe. In terms of overall power he's powerful enough to easily one-shot opponents as powerful as Beerus and is capable of casually defeating the likes of Goku and Vegeta with neither managing to land a hit on him during sparring matches. Whis is also perhaps the most versatile combatant in DB, possessing abilities such as Time Manipulation, Teleportation, Matter Manipulation, Dimensional Control, Magic Materialization and perhaps even more.