What I suddenly remember

There are strong and weak memories, and even memories that can not be remembered. I think we have to care about strong memories. Often suddenly some memories come up, and we don't know why. But that phenomenon must have meanings. Brain always work and organize memories. all memories are stored but not everything is needed.
Recently, I remembered my old acquaintances of elementary school. He moved before graduation, and I only remember him talking about nuclear power very proudly. And he lost almost all teeth because of cavity.
and one more memory, 1 year older guy who was really bad, his brother was the boss of bike gangs.　I lent him a book featuring Pokemon and he returned it washed in washing machine. He was really irritating.
But does all these memories have important meanings???? I don't think so but there must be.
Also, what we dream contains meanings from unconcious. this makes sense because when we sleep, our concious does not work. But when we awake what produces that memories suddenly appear.
What part of our brain organize memories???