The Elders choose Jonas to be the Receiver of Memories. He will receive memories from the past which will change his whole life forever.
Jonas first meets the Giver and they talk about how important it must be to have someone to have memories of the past to give information to the Elders.
The Giver gives Jonas one of the memories of the past and what the weather since now there is climate control. Jonas begins to realize how great the past was before their perfect community.
With the memories he was given he was trying to expose what the elders were hiding. His friends stayed away from him because he was acting different ever since he became the Receiver of Memories.
Jonas runs away from the community with Gabe because he was going to be released which means killed because he has a twin. He gets past a limit which holds the memories away. Once he gets passed the limit, the memories that were past are now present.
Once Jonas and Gabe passed the limit of the shield of memories has been broken. Everyone in the community got the memories in the past which are now the present. Now there is love real love, not the love when you get selected to be with a partner. The memories show what the world used to be like before the community was built.