You need to cite in general to give credit where it is due. For in text citations, it helps readers know where you got the information from which sources which you have in the bibliography, and this helps readers know which sources to use to learn more about the information you presented by going to the citations list/bibliography at the end.
An in-text citation shows where you've quoted or paraphrased another person's work. Always give credit to the original writer to avoid plagiarism. In-text citations direct the reader to the full source entry in the bibliography, works cited or reference list.
Characterization is when the author introduces his character(s). So I guess when you’re asked that question it means you have to find the character’s behavior, personality, appearance, thought process... etc
