Selina Kyle aka Catwoman is primarily a thief who resides in Gotham City. She's not just any thief, Catwoman is arguably the best and most lethal solo thief in the city. To some, she's regarded as a villain and enemy of Batman but to most of us, she would fall in the antihero category. We've all seen how Batman has a soft spot for her. Catwoman's allegiance is mostly good because she has been an ally of the Batman family on numerous occasions.
Selina's transition to becoming a thief started at a very young age. When she was a kid and following the imprisonment of her father, Selina and her brother were put in separate foster homes, where Selina lived with her caretaker Miss Oliver in the Oliver's Group Home. Miss Oliver taught the kids under her care to steal for her; which is where Selina developed her initial thieving skills. She was soon caught stealing and brought in by the Mayor to work in his office. As soon as she was cleared from the accusation, she decided to start searching for her brother, only to find that she wasn't who she thought she was. Looking through her files caught the attention of some people who wanted the truth to be kept a secret; they tried to get rid of her by pushing her off a roof top. She survived, realizing that everything she has ever known wasn't what it seemed. A few months later, she took the role of Catwoman and thus, her story began.
However, in the more popular depiction of Catwoman's origin, she was an orphan girl who lived on the streets with a group of other homeless people. In one version of the origins, one of her fellow homeless friends was Ivy Pepper, who would later become Poison Ivy. In this origin, even as a kid, Selina was always seen as a solitary explorer of the City of Gotham. She learned how to steal and petty thefts was her main means of survival.
As she grew up, Catwoman learned various skills in aid of her thieving expertise. She was highly stealthy, good with disguises, had advanced melee combat skills, and very athletic and acrobatic. She even learned how to use firearms and a variety of other weapons like daggers, knives, swords, sticks, etc.. Selina was most closely associated with her bullwhip. In some versions, Catwoman was also multi-lingual.
Catwoman's first appearance in a movie was in the 1992 Batman Returns. Following the success of Selina Kyle's character in the movie, Catwoman was given her own comic book series from the year 1993 onward. Her success in the movie was also a stepping stone to her debut and then multiple appearances in Batman: The Animated Series. Wielding her bullwhip in both TV appearances, Selina Kyle is shown to operate at her own will and with her own rules. Her disregard for the law further popularized her character and she became one of the favorites of Gotham City, later having her own movie Catwoman in 2004, and then appearing as a dominant side character in the Dark Knight Series.