We have what is called as sensor memory, short term memory and long term memory. Memory is a result of formation of connections among neurons. Neurons in brain are spread throughout the brain.
Sensor memory is stores what is seen/felt/smelt/heard through the senses for a brief period of time.
Short term memory is what is remembered for a minutes to a few weeks. The short term capacity is not large. The content in short term memory is remembered as it is, in general. Much analysis may not have been done. Associations among neurons is done but not strongly and permanently. These associations are temporary and transient or unstable. The short term memory is managed by frontal and parietal lobes.
Long term memory, on the other hand, is the result of stable associations and links formed among neurons. It is based on the semantic meaning of the fact memorized. Hippocampus in the brain helps in this process. The various aspects like where, what, why, how etc. of the fact are stored along with the fact. Also, the event that caused the fact is remembered. Thus the number of neurons and their associations are more. The information can be retrieved in many ways. Further, repetition of facts many times in course of time increases long term memorization.
For long term memorization requires a good understanding of the fact through its analysis, and repetition and recalling of the fact many times. Hippocampus in the brain helps long term memory.