Many have struggled to try to find an adequate definition for memory.
Perhaps the best definition of memory is "the modification of behavior by experience."
Without memory, we could have no past and no intelligence or ability to learn by experience. We would constantly be relearning and discovering things day in and day out.
Memory involves the "making of an impression by an experience, the retention of some record of this impression and the re-entry of this record into consciousness (or behavior) as recall and recognition."
The process of making a memory occurs in all experiences whether or not
we are consciously aware of this. Information can be retained and
recalled without it needing to enter conscious awareness.
Information that becomes the most firmly fixed and that is retained for the longest amount of time usually consists of youthful, repeated, or vivid experiences. The process of forming a memory from these experiences is gradual. Many studies done on the fixing of memories have proven that considerable time exists between the arrival of incoming information in the form of nerve impulses and the fixing of a memory trace.