The Giver is an example of a dystopia. A dystopia is a world that seems perfect on the outside, but is actually rotten on the inside. Authors write dystopias to point us to specific themes or lessons. Since you are asked to write a paragraph, it sounds like listing the themes might be the best approach.
First of all, what do you think the author was trying to say with this story? What point was she trying to get across? That is a theme. For example, the community is very concerned with sameness. Differences are not tolerated, and difference is actually feared. It is this fear of difference that leads the society to make so many rules so that everyone is the same. Jonas is different, and this isolates him from his friends and family. Yet he is a sensitive, wonderful boy. The lesson: Difference should be celebrated, not feared!
Another way to try to determine themes is to ask yourself what lessons the main character learns. Jonas’s society tries very hard to keep people from being uncomfortable in any way. They are sheltered from pain, and they bad memories taken from them. They also don’t want identical twins, because people might get confused and be uncomfortable. The result: One newborn twin is murdered because it is smaller! Jonas is horrified. He learns that denying difference can have consequences.
So there are two themes for you. Difference should be celebrated, not feared! Denying difference can have consequences. Think of a few more to include in your paragraph. If you get stuck, I have included links to more themes. I am hoping I got you on your way by not just telling you themes but also telling you how to find them!