A Padawan, Padawan learner, or Jedi Apprentice in Basic, was a child, or in some cases an adult, who began serious training under a Jedi Knight or a Jedi Master, chosen by the Knight or Master him/herself from the ranks of the younglings.
Padawans followed and helped their Masters everywhere, unless seen unfit by the master, from simple tasks to dangerous missions, so that they learned from experience and personal guidance. Padawans that belonged to species that grew hair on their heads typically grew a braid signifying their apprentice status, although there were a few exceptions among species, even some humans. When a Padawan passed the 'trials', he or she was elevated to knighthood, and his or her braid was cut off during the knighting ceremony. There was no fixed age when this happens: Padawans could even be adults, but for a Human, it usually occurred in the Padawan's early- or mid-twenties.
If a youngling was not chosen by any Jedi Knight to be his or her Padawan by thirteen years of age, the youngling was placed into another, lesser role in the Jedi Service Corps—a tradition abandoned by Luke Skywalker when he created the New Jedi Order.
There were multiple ways for a Padawan to be chosen by a master. Every so often tournaments were held within the Temple that allowed students to compete against each other in order to prove themselves worthy of apprenticeship in the eyes of visiting Masters. Obi-Wan Kenobi once competed in such a tournament to win the favor of Jedi Master Qui-Gon Jinn. Occasionally a master would develop a bond with one of the temple students and request to become their master. Other times, they would outright declare that they would train the student if the Council did not approve, as Qui-Gon Jinn, and later Obi-Wan Kenobi, would do in order to take Anakin Skywalker as their apprentice. Once more a student may also be assigned to a Master by the Council as was the case of Ahsoka Tano's apprenticeship to Anakin Skywalker.
There was one unique instance in which a Padawan was selected as part of a wager, when Yoda bet Jai Maruk that if Tallisibeth Enwandung-Esterhazy won the Temple Apprentice Tournament, Maruk would have to take her as his Padawan. Esterhazy won, and Maruk fulfilled his end of the bet by making her his apprentice.
After being selected, each apprentice would go to one of the four Rotunda chapels in the Temple. There, they would meditate alone for a night, before going off to meet their new master.
The terms "Jedi Apprentice" and "Padawan" were not always synonymous throughout the long history of the Jedi Order. Nor were the terms used consistently throughout the thousands of years of the Jedi Order.
Before the Old Sith Wars, the practice of multiple apprentices learning under a single Master was common. During this period most students were simply called Jedi Apprentices until they achieved the rank of "Knight." After this time, training multiple students concurrently was discouraged, due to their apparent predilection to defect to the dark ways of the Sith. Thus, while ancient masters such as Arca Jeth commonly had several apprentices at any given time, tradition came to dictate a single Padawan, allowing his or her master to better focus on their pupil, and give them more of their attention. The term Padawan usually indicated the new practice of one student to one master.
During the Mandalorian Wars and the Jedi Civil War, the rank of "Jedi Apprentice" was actually obtained before the rank of Padawan. During this time, an Apprentice mostly trained within the safety of the temple and could learn from many instructors there. After completing some relatively easy trials, the Apprentice would be granted the rank of Padawan and be able to train with a master during real world missions. The Jedi Apprentices stage at that time closely resembled the "Jedi Youngling" stage of training that was common just before the fall of the Jedi order. Using the word "youngling" to describe these Jedi Apprentices would have been inaccurate, however. The many years of war and loss of life necessitated that many beings be allowed into the Order at older ages. It was not uncommon for adults to be apprentices at that time. For example, Revan, after losing his memory and being "reprogrammed" by the Dantooine Enclave Council, was retrained as a Apprentice under Master Zhar Lestin, and was then granted the title of Padawan. With additional guidance from Bastila Shan, he was quickly promoted though the ranks due to the urgency of his mission and his unique situation.
In later years, the terms "Jedi Apprentice" and "Padawan" became synonymous. The period of training limited to the temple was often called the "Youngling" stage. This change in terminology reflected the increased importance that the Jedi placed on only training students who started at a very early age. Anakin Skywalker was an exception to the strict age limits that the later Order enforced. He became a Padawan under Obi-Wan Kenobi without ever training as a youngling, due to his relatively advanced age of ten years. When his son, Luke wished to start training under Grand Master Yoda, his advanced age of 20 was a big concern. But, as happened during past wars, Yoda decided to not enforce the age limits in that time of great need as well.
After the Great Jedi Purge, several early Jedi that eventually formed the New Jedi Order never had the "rank" of Padawan, since there were no Masters to train them. Among these were Luke Skywalker, who was privately trained by Jedi Master Obi-Wan Kenobi and Grand Master Yoda, and Kyle Katarn, a Force-sensitive who was self-taught with guidance from Qu Rahn's Force ghost.
When Skywalker established the New Jedi Order, things were quite different: the traditional Padawan's braid, as well as the term "Padawan" itself, disappeared at this time. The New Jedi Order used the term "Apprentice" instead.
Due to the small number of Jedi Knights, Luke Skywalker loosened the restrictions on the number of apprentices a Jedi could train at once. Skywalker, for example, simultaneously mentored his nephews Jacen and Anakin Solo. The problems of this new system soon became apparent, since the Master could not pay full attention to both his students—an example of this would be Kyle Katarn's students Jaden Korr and Rosh Penin (who turned to the dark side for a brief time), so this rule may have been replaced with the original rule, but this is yet unknown.
The term Padawan first appeared as far back as George Lucas's first story treatments for Star Wars. However, it was not heard before Star Wars Episode I: The Phantom Menace was filmed; in all previous works, the concept was called "Apprentice."