How does are brain remember things from way in our past and how does it decide what to remember and what not too?

Question: How does are brain remember things from way in our past and how does it decide what to remember and what not too?
- Keywords:
  brain,
  decide,
  past,
  remember
Asked by barnesy to Tatiana, Priya, Natt, Dwaine, Andy on 25 Jun 2015.
- Priya Hari answered on 25 Jun 2015:
  
  I don’t know the real answer to this question as I have not really studied the brain but just from personal experience I can say that our brain is more likely to remember things that have had a significant impact on our lives because it is associated with an emotion. For example, you might remember a great meal you had at christmas because you really enjoyed it and you were with your family but you might not be to remember what you had for dinner last week, because it was just a normal dinner. The brain also remembers things that you have seen or heard repeated, hence it is important to keep going over your notes when you are revising.

Question: How does are brain remember things from way in our past and how does it decide what to remember and what not too?