Darth Vader, born Anakin Skywalker, was a Dark Lord of the Sith and the right-hand man of Emperor Palpatine. He eventually turned against his master at the Battle of Endor in order to save the life of his son.
Anakin Skywalker was born into slavery on the planet Tatooine, where he spent much of his life as the property of a junk dealer named Watto. Jedi Knight Qui-Gon Jinn met the boy in the junk shop while looking for parts to repair Queen Amidala's yacht. Anakin offered to help the Queen by winning a podrace, the winnings of which would cover the cost of the parts needed to repair the yacht. In a side bet with Watto, Qui-Gon Jinn arranged to have Anakin released if he won the race, which he did. Anakin played a pivotal role in the Battle of Naboo, when he accidentally flew a Naboo starfighter into the hangar of the Trade Federation's droid control ship; from inside the shields, he was able to destroy the ship's main reactor, destroying the ship and disabling the Trade Federation's droid army on the ground.
Anakin Skywalker trained to be a Jedi under Obi-Wan Kenobi. During his training, Supreme Chancellor Palpatine also served as a mentor and confidant to him. He completed the Trials sometime after the Battle of Geonosis to become a Jedi Knight. He served as an officer in the Grand Army of the Republic during the Clone Wars. During this time he earned the honor name Tan, probably for his piloting skill. He also earned other titles, including his most famous "The Hero Without Fear." Promoted to the rank of General, he served as one of the commanders of the famous Open Circle Fleet. At the Second Battle of Coruscant, he out-fought Count Dooku, the man who had taken his right hand at Geonosis.
At the close of the Clone Wars, Anakin Skywalker apprenticed himself to Darth Sidious in hopes of learning a Dark Side technique that would allow him to prevent the death he had foreseen for his wife, Padmé Amidala. Taking the name Darth Vader, he led an assault on the Jedi Temple and helped murder every Jedi there. He then journeyed to Mustafar, where he assassinated the remaining leadership of the CIS. Padmé followed him to Mustafar, inadvertently bringing Obi-Wan Kenobi with her. Obi-Wan defeated Darth Vader in a duel and left him for dead.
Emperor Palpatine reached Mustafar in time to rescue Vader. With extensive bionic assistance, Vader survived to become Palpatine's most important servant for the duration of the Empire. He eventually turned against his master and killed him at the Battle of Endor.
As a Jedi, Anakin Skywalker had tremendous power, but surprisingly little skill. He was adept with telekinesis and achieved mastery with the lightsabre, but he never achieved great proficiency with many other Jedi skills, such as precognition. In combat, he relied on strength, agility, endurance, and his strong affinity for the Force to overwhelm opponents.
As a Sith, Darth Vader retained much of his affinity for the Force and further developed his telekinetic skills, but he still never developed other Force skills fully. His cyborg body was stronger than his original body, but less agile, and he relied more on physical strength to batter his opponents into submission in combat. He never mastered the Sith technique of Force lightning.
- To be fair, the Young Anakin performance can't really be blamed on Jake Lloyd, who was 11 years old at the time. The responsibility falls on George Lucas, who did the writing, casting, and directing.