In the oz land, a witch is a creature that can control the magic and the other creatures magics or not. the good witches are protectors, and the wicked witches are controllers.
Good and Wicked Witches are witches associated with the four cardinal directions and the four separate countries of the Land of Oz who have chosen if they follow the path of good or wickedness.
The wicked witches are vulnerable to water, like was shown in The Wonderful Wizard of Oz.
In Baum
In his first Oz book, The Wonderful Wizard of Oz (1900), L. Frank Baum famously created good witches in the north and south of Oz and evil witches in the east and west. The Wicked Witch of the East ruled the Munchkin Country, while the Wicked Witch of the West dominated the Winkie Country. Dorothy Gale met the Good Witch of the North, from the Gillikin Country, early in her first stay in Oz (Chapter 2). Glinda is identified as the good "Witch of the South" (Chapter 18), though in later books she is generally called a sorceress rather than a witch. She is consistently located in the Quadling Country.
Baum left his Good Witch of the North unnamed in his original book; but in his 1902 stage adaptation of the book he called her Locasta.
The author killed off both of his wicked witches in his first Oz book; when he came to write his second, The Marvelous Land of Oz (1904), he needed a new villain, and produced Mombi, the Wicked Witch of the North. For the first time, both a good and an evil witch were associated with one of the cardinal directions.
Baum added another level of complexity to his scheme in his fourth book, Dorothy and the Wizard in Oz (1908). At one point, Princess Ozma explains that there had previously been wicked witches in all four quadrants; in addition to the two destroyed by Dorothy, "a good witch had conquered Mombi in the North and Glinda the Good had conquered the evil Witch of the South" (Chapter 15).
Baum added others villains, witches (like Blinkie), Yookoohoos, and other magic workers in later books, but did not amend his large-scale yet still incomplete fourfold scheme, of four evil witches and two good ones.
In Thompson
Ruth Plumly Thompson, Baum's successor as Royal Historian of Oz, made two significant additions to this scheme. Most significantly, she created Gloma, the witch-queen of the Black Forest, in The Wishing Horse of Oz (1935). Gloma, if not precisely the Good Witch of the West, is at least a good witch in the west.
Thompson also created Tattypoo, in The Giant Horse of Oz (1928), as her version of the Good Witch of the North.
Later authors
The remaining gaps in the larger fourfold plan tempted the talents of later Oz writers. Rachel Cosgrove Payes took up Baum's hint and created Singra as the Wicked Witch of the South in her novel The Wicked Witch of Oz, a book written in 1952 but not published until 1993.
Eric Shanower draws his own, unnamed Wicked Witch of the South in his first Oz graphic novel, The Enchanted Apples of Oz (1986). In his fifth Oz graphic novel, The Blue Witch of Oz (1992), Shanower accepts Thompson's Gloma as the Good Witch of the West, and then creates his own Good Witch of the East in the person of Abatha, the Blue Witch of the Munchkins.
In his 2000 novel The Unknown Witches of Oz, David Hardenbrook accepts Locasta as the Good Witch of the North, but adapts the character to his own purposes.