Master Yoda

"Size matters not. Look at me. Judge me by my size, do you? Hmm? Hmm. And well you should not. For my ally is the Force, and a powerful ally it is."
―Yoda, to Luke Skywalker

Yoda was one of the most renowned and powerful Jedi Masters in galactic history. He was known for his legendary wisdom, mastery of the Force and skills in lightsaber combat. Yoda served as a member of the Jedi High Council in the last centuries of the Galactic Republic and reigned as Grand Master of the Jedi Order before, during and after the devastating Clone Wars. Following the First Battle of Geonosis, Yoda held the title of Master of the Order in addition to that of Grand Master. In his centuries of service to the galaxy and the Force, Grand Master Yoda had a hand in the training of nearly all the Jedi in the Order, including such luminaries as Obi-Wan Kenobi, Ki-Adi-Mundi and Oppo Rancisis; all of whom would come to serve on the Jedi Council along with him.

Obi-Wan Kenobi

"Obi-Wan is a great mentor; as wise as Master Yoda, and as powerful as Master Windu."
―Anakin Skywalker, to Padme Amidala

Obi-Wan Kenobi, later known as Ben Kenobi during his exile, was a legendary Jedi Master who played a significant role in the fate of the galaxy during the waning days of the Galactic Republic. He was the mentor of both Anakin and Luke Skywalker, training both in the ways of the Force. He had a long and tumultuous career that helped shape the fate of the entire galaxy.

Darth Vader

"You were the Chosen One! It was said that you would destroy the Sith, not join them! Bring balance to the Force, not leave it in darkness!"
―Obi-Wan Kenobi, to the fallen Anakin Skywalker

Anakin Skywalker was a Force-sensitive Human male who served the Galactic Republic as a Jedi Knight and later served the Galactic Empire as the Sith Lord Darth Vader. Born to the slave Shmi Skywalker in 41.9 BBY, Anakin was concieved by midi-chlorians, the symbiotic organisms that allowed individuals to touch the Force, and he and his mother were brought to the desert planet of Tatooine to be the slaves of Gardulla the Hutt. They soon ended up as the property of the Toydarian Watto, and Skywalker exhibited exceptional piloting skills and a reputation for being able to build and repair anything even at a young age. In 32 BBY, Skywalker encountered the Jedi Qui-Gon Jinn and Padmé Amidala, and he helped them secure the parts they needed for their starship by winning the Boonta Eve Classic podracing event—only to learn that he had also won his freedom in doing so.

Text Source: StarWars Wikia