Please be warned if you haven't read these books these sections contain plot-spoilers.
Plot Summary: The book, set in the fantasy kingdom of Tortall, follows Alanna's growth as a page in the royal court, where she keeps her gender a secret, while learning to fence, fight, ride, and study alongside the male pages. Alanna befriends the heir to the throne and the charming King of Thieves, copes with the magical power she possesses and her mistrust of it, faces the palace bully, struggles with her suspicions of the prince's cousin Duke Roger, and finally travels to the southern desert, where the Bazhir tribesmen guard a Black City that has invaded her dreams. There, she and her friend Prince Jonathan defeat the much-feared Ysandir, a race of demons that has kept the Black City captive for generations. In the process, Jonathan learns that Alanna is a girl. Despite this, he chooses her as his squire when he has become a knight.
Alanna of Trebond - The main protagonist of the series, who hides her real sex to be able to train as a knight.
Thom of Trebond - Alanna's twin brother, who detests fighting and prefers magic; he goes to the City of the Gods to learn how to be a powerful mage.
Coram Smythesson - Alanna's first teacher of fighting and hunting at Trebond, he accompanies her to the capital as her manservant; one of the few who know her true sex.
Jonathan of Conté - the heir to the throne of Tortall and the King and Queen's only son, Alanna's best friend at the palace; a few years older than Alanna.
Gareth the Younger of Naxen (a.k.a. "Gary") - one of Jonathan's and Alanna's friends and Jonathan's cousin, easygoing and funny, he acts as her sponsor when she arrives.
Duke Gareth of Naxen - the man who oversees training of the pages and squires, Gary's father.
Roger of Conté - Jonathan's adult cousin, a powerful magician and second in line for the throne; Alanna mistrusts him but has no evidence to support her suspicions, Jonathan trusts him completely
Ralon of Malven - one of the pages who bullies Alanna when she arrives; she eventually bests him in a fight and he leaves the palace in furious disgrace
Moonlight - Alanna's horse, trained for combat; George bought the horse and sold her to Alanna at a low price
Info from: Wikipedia