the characters are just the people in the story. The setting is where it happens, so if it mainly happens in a school, that would be the setting. The problems could be like two of the characters hating each other or someone's mom sick in the hospital, stuff like that. problems like these usually get solved at the end of the story but they might not, like a cliffhanger.
Then "How are they like other stories you've read?" You can just take any other stories you know and look for things that are the same in both of them. Like if there's a character who's really shy in the story you read for class and the story you read on your own, then you would say " In this story, a character named Mia is really shy. In a story I read on my own, Social Caterpillar, Nicky is really shy and quiet."(Just a fake example) You would do the same thing for the setting and problems.
HIV is often thought of as the most widespread in infection counts of all these and is more widely known than the others in those terms HIV is the answer.
