Sakura Kinomoto is a young girl who accidently releases the Clow Cards from a mysterious book in her father’s basement. She then meets Cerberus who makes it her mission that she returns the spirits into Card form. She then must turn the Clow Cards into her own Sakura Cards so that they keep their powers.
source: Zerochan; written by Bootan
Also see Kinomoto Sakura (TRC) for an alternate universe version of the same character.