Before she became known as the White Witch, she was referred to as Jadis, as she was in "The Magician's Nephew." She was the last Queen of Charn, which she herself destroyed. Jadis arrived in Narnia with Digory (Young Professor Kirke) and Polly in "The Magician's Nephew" and has taken over the land as the White Witch in "The Lion, the Witch, and the Wardrobe." Completely evil, she is also very dangerous, even in "The Silver Chair."
She is also mentioned in "The Horse and His Boy" by the Grand Vizier Ahoshta Tarkhaan (who Aravis Tarkheena was supposed to marry) as "a most powerful enchantress." These Calormenes (people from Calormen, land south of Narnia) were evil too, but believed without knowing that Narnia at the time the Tisroc ruled were hateful to the gods. The most important god for them was Tash (who Aravis's great-great-great grandfather Ardeeb Tisroc was supposedly descended in a right line from) and others were Azaroth and Zardeenah, Lady of the Night and of Maidens. When the Tisroc (Prince Rabadash's father) began his rein, the land of Narnia was under the rule of the Pevensies. Before that they knew it was covered with ice and snow and was ruled by some enchantress. Tarkheena Lasaraleen (Aravis's vain and selfish friend who despite those qualities helps her escape to Narnia) thought that even during Aravis's time Narnia was still a country of perpetual snow and ice inhabited by demons and sorcerers. As Prince Rabadash said they knew that presently The White Witch is dead which wasn't true, she was defeated, but not entirely dead as she could live forever. They also knew that the ice and snow have vanished so that Narnia is full of lush again. They knew that the changes were caused by the Kings and Queens of Narnia (the Pevensies), but they thought they were the evil ones not The White Witch. Prince Rabadash thought that the changes could have been from natural causes but the Tisroc did not and convinced him so. Also, they knew that defeating The White Witch was done with the aid of magic. They knew of Aslan too and thought he was "a demon of hideous aspect and irresistible maleficence who appeared in the shape of a lion" who supported Peter High King of Narnia (whom their gods utterly reject). They are not entirely stupid as they know Narnia is strong and fear it. She is also mentioned occasionally as the Witch and "the Winter" is added. Bree also mentions her as "the Witch" because he told Aravis he knew the lion, Aslan, drove away the Witch and the Winter.
She appears in "Prince Caspian" the movie for a brief time.