Direct characterization is characterization done by the author in which specific details are told. So for Rachel and Brick the reader is told that each character is a boy or girl. The reader is told that they are both 11 years old. The reader is also told things about their race and skin color.
Indirect characterization is done when the author gives details about a character's traits by writing about their thoughts, words, and actions. How other characters treat that person also gives readers insight into what a character may be like. In the novel the reader comes to understand that Rachel feels she is a bit of an outcast. The black girls at school think her skin is too light and that she is too pretty. That simple detail tells the reader that she's cute and that she doesn't have very many close female friends. Brick also has self confidence issues as indicated by his name change to something that he believes sounds stronger. He is also looking for acceptance and love, which can be shown by his running away from home and constantly moving from place to place.