Sometime in the past, Jonas's community decided to give up their memories in order to eliminate the pain and regret that came with them. They were trying to create a totally peaceful and harmonious society without conflict, war, or hate by eliminating emotion entirely. They succeeded: the community is almost perfectly stable and totally safe. Yet Jonas realizes that without memories, a person can't learn from mistakes, celebrate accomplishments, know love or happiness or any other deep emotion, or grow as an individual.
In The Giver, memory doesn't function as it does in the real world. Certain people have the power to transmit memories to others, and this ability is connected to the trait of blue eyes, which Jonas, The Giver, and Gabriel all share. Memory is also not just a mental exercise. Instead, it's an actual experience: Jonas literally feels the cold when he remembers snow. Finally, when a keeper of memories, called a Receiver, dies or leaves the community, all of his or her memories are released to the community. By bestowing upon memory these magical properties, Lowry emphasizes memory's preciousness and its power to influence, guide, and enrich life.