The Batgirl was first introduced to the Batman mythos because they needed to add a girl to the hero cast. There were many unwarranted remarks regarding homosexuality between Batman and Robin. Her name was Betty Kane, the side kick to Kathy Kane, Batwoman. After a while they removed her because of declining sales. It wasn't until many years later where Batgirl was reintroduced to the popular origin story of Barbara Gordon. When Barbara disrupted the kidnapping of Bruce Wayne, he was impressed and appointed her to become Batgirl unknowingly to her father, Commissioner Gordon. When she proved more popular as Batgirl than the previous characters, she became a regular character.
The role of Batgirl was also temporarily taken up by the Huntress in the story arc "No Man's Land". Yet another woman has taken the role of Batgirl, her name is Cassandra Cain, a martial arts child prodigy who is partly Asian. She uses the same costume that was worn by Huntress when she was previously the Batgirl. She was trained by
assassins at an early age and can't read or write. She is able to communicate with body language and is skilled in reading movements both in fighting and in normal or dangerous surroundings. This makes her an excellent detective and is able to know when something isn't right when walking into a room. She temporarily became a villain, but it was only because of a mind altering drug given to her by Deathstroke. During her absence as Batgirl in this time period, her role was temporarily take up by Charlotte Gage-Radcliffe, a young girl with superpowers. Once Oracle found out about this new Batgirl she spoke with Charlotte and they agreed she would give up being Batgirl.
During the story arc R.I.P Batman. Bruce Wayne is killed while on a mission with the JLA as the Bat-family are left in a state of crisis Gotham city descends
into chaos with it's dark knight no longer protecting it. While Dick Grayson and Jason Todd battle it out for the Batman Cowl Cassandra meets a up with Spoiler(Stephanie Brown) and together they take down minor thugs while on patrol. Finally deciding her fate Cassandra takes of her outfit and hands it to Stephanie saying "I fought for him. But no more"
After the events of R.I.P Batman a new Batgirl takes up the mantle. While juggling her normal life and keeping her night-time adventures secret from her mother Stephanie continues to fight crime as the latest Batgirl. Although the current Batgirl, Oracle the original Batgirl intervenes and tries her best to stop Stephanie from taking up the mantle. Untrusting of each
other first both Stephanie and Oracle settle their differences after Stephanie's battle with the Scarecrow and eventually convince the new Batman and Robin that she is worthy of taking up the mantle. Continuing her stay as the new Batgirl and taking on villains like Scarecrow,Calculator and even her very own rogue's gallery Stephanie has truly proven her worth as a member of the Bat-Family.