There are many themes within the novel that relate to understanding others. As other respondents have mentioned, characters such as Mayella, Boo, even Tom Robinson and Calpurnia are all representations of the "other" to Scout (The "other" defined as anything that is not the self or that is outside of the norm for the self). Put yourself in Scout's shoes, and then ask yourself if there are any people or groups of people that touch your life in any way that are "different" from you. How do you relate to them? Are your opinions of them formed by sterotypes? If so, are these opinions negative, and if they are do they actually match the individuals in question? These are the types of questions that you should ask yourself, for these are the things that Scout learns about. She is afraid of Boo at the start because of what she has heard about him, but she revises her opinion at the end. This is not the only change of perception that she experiences. Have you ever had a change of perception about someone?
You tagged To Kill a Mockingbird in this question. This leads me to believe you are being asked to answer your question after having read about characters who struggle with understanding.
Think about how Scout has been in the position to deal with so many characters who hurt her either knowingly or unknowingly. She had kids reference her father as a "nigger-lover" and had to hold her cool. She had to watch Mayella Ewell on the witness stand and draw her own understanding conclusions. She references "standing in someone else's shoes".
How have you had to hold your cool in your life? Have you had to try to understand where someone else is coming from? Have you thought to look at a situation from someone else's perspective? These are questions you should answer.
Surely this is something that you are going to have to answer for yourself because the kinds of issues that we have (those of us who answer questions on here) are issues that you are not so likely to have given that you are so much younger than we are.
For me, I have to work on understanding others mainly when I deal with my children and students. I need to realize what sorts of motivations they have and what kinds of issues they are facing that make them act in the ways that they do. This, of course, would not apply to you. Although maybe you could turn it around and think about teachers and parents...