The White Witch of Narnia was not the rightful Queen of Narnia. She knew of the prophecy:
When Adam's flesh and Adam's bone
Sits in Cair Paravel on throne,
The evil will be over and done.
In other words, humans (the children are sons and daughters of Adam and Eve, the first humans) are a threat to the witch. There are four thrones at Cair Paravel, and there are four children. As far as the White Witch is concerned, they must not be allowed to be kings and queens of Narnia, because then her own rule would be over.
The White Witch ordered Maugrim to capture and kill any humans that entered Narnia, particularly the Pevensie children. She saw humans as a threat to her power and wanted them eliminated to maintain control over the land.
The White Witch in Narnia was watching for humans because of a prophecy that foretold that humans would play a role in ending her reign. She feared the arrival of the sons of Adam and daughters of Eve as they posed a threat to her power.
Tilda Swinton played the White Witch in the first movie: The Lion the Witch and the Wardrobe.
The creatures in Narnia felt nervous about humans because they had never been around them before. The Chronicles of Narnia fantasy novels were written by C.S. Lewis.
The White Witch is named Jadis. She was brought into Narnia by Digory Kirk and Polly Plumber from a different world called Charn, and she made Narnia so that it was always winter. The White Witch appears in the following Narnia books:The Magician's NephewThe Lion, the Witch and the WardrobePrince CaspianVoyage of the Dawn TreaderThe Silver Chair
Jadis of Charn, aka the White Witch.
Her name was Jadis the White Witch.
Aslan
Her name is Jadis, but is known to most as the White Witch.
In the Narnia movie series, the character of the White Witch, who is the antagonist and queen of Narnia, was played by Tilda Swinton in "The Lion, the Witch and the Wardrobe" (2005) and Jadis (the White Witch) in "The Chronicles of Narnia: The Magician's Nephew" (which hasn't been released yet).
Edmund committed the crime of treason. He betrayed his brother and sisters to the White Witch, telling her that they were in Narnia, and giving her the necessary information so she could capture them.
The White Witch