Engram is the hypothetical physical unit where the new memory is stored. For example, if we learn a new information, some changes occur in the brain as a part of storing the new information entered into the brain.
However, several scientists believed that the memory storage process is distributed throughout the brain and provided better explanations than do engrams.
For example, the organs associated with the explicit memory are, medial temporal lobes (especially the hippocampus and amygdala), thalamus, fornix, prefrontal cortex. Thus, the medial temporal lobes are required for the memory retrival.
Implicit memory or the non-declarative memory involves the unintentional remembering. The amygdala is associated with the non-declarative memory.