Memory is a crazy thing. I find it fascinating that often times we can vividly recall events from years ago. Incidentally the ability to for memories is not something that we are born with. At birth, your brain beings to shape itself based on the interactions that you have with your environment. Slowly but surely your brain branches our and begins making new connections and then the neurons in your brain begin recording experiences.
These recording are what we call memories. There ar two types of memorization, and their processes are completely different. There is rote memory, where one is able to memorize facts and data. What we often think of are autobiographical memories.
The primary memory circuit is called the hippocampus. When it works well, every moment of your life is registered. If it is damaged, it can be a struggle to remember facts and event. In a case of severe damage to the hippocampus, your most basic memory functions will suffer, causing someone to forget names, directions to places they have been hundreds of times, and more.
Why is memory important? It is one of the things that defines us as humans. One of the reasons that we care about tomorrow is because we remember yesterday. Memory helps with abstract thought, creativity, and problem solving.
If you think about it, memory is essential to survival of our species as we know it.