Memory helps make individuals who they are. Without the help of memories, someone would struggle to learn new information, form lasting relationships, or function in daily life. Memory allows the brain to encode, store, and retrieve information in three basic forms.
Humans process stimuli first with their sensory memory; that information is typically held in the brain for less than a second, which may explain why most people report that when shown an object quickly, they feel like they take in more details than they're able to recall later. Next, the information is transferred to the short-term memory or working memory, which allows someone to mull things over and hold key information in their mind. Finally, people store past events and patterns in their long-term memory, also known as episodic or semantic memory.
Different areas of the brain affect different aspects of memory. The hippocampus, for instance, is related to spatial memory, which helps the brain map the surrounding world and find its way around a known place. The amygdala, on the other hand, is linked to emotional memory.
Research is being done on the genetics of memory—and particularly a possible genetic root for Alzheimer's disease—but the science is still preliminary; it's hard to know why some people remember things much more efficiently than others.