The adventures of the original Supergirl, Kara from Krypton, were published by DC Comics from 1959 to 1985. She appeared in Action Comics, Adventures Comics, Superman Family, and two Supergirl series (see Silver Age Comics). In 1984 she starred in her own SUPERGIRL movie. Kara died in the Crisis on Infinite Earths comic series which rebooted the DC universe in 1985.
In the post-Crisis universe Kara never existed, and her place was taken by a new Supergirl known as Matrix, an artificially created shapeshifter who was created from the genetic matrix of another universe’s Lana Lang. Matrix physically merged with a human girl named Linda Danvers in the 1996 Supergirl series, gaining a human identity and a new family and set of friends who didn’t know about her new powers. Supergirl also gained special new powers as an earth-born angel. Linda Danvers retired from being Supergirl at the end of her series in 2003.
A modern version of Kara has been appearing in DC Comics since 2004. An animated adaptation of her origin story has been released on DVD as Superman/Batman: Apocalypse. Kara starred in her own Supergirl series until her character and series were rebooted again in fall 2011 as part of DC Comics’ company relaunch (The New 52).
A cute younger version of Supergirl appears in the kid-friendly series Tiny Titans. Another all-ages take on Supergirl appears in the miniseries Supergirl: Cosmic Adventures in the 8th Grade.
Supergirl is well known outside comics from her appearances on the Superman and Justice League animated TV series.
Kara also appeared on TV’s Smallville throughout Season 7, in the Season 8 episode “Bloodlines”, and in the Season 10 episodes “Supergirl” and “Prophecy”.
Power Girl is Supergirl’s counterpart from the alternate universe of Earth-2. She has her own story and background and is closely connected to the Golden Age superhero team the Justice Society of America.