Notes and researches.
Memory is not one, holistic resource present in our minds. Functioning 'memory' is in fact composed of several different systems and subsystems that work together to deliver us functioning data with which we can think and act. These systems form a sort of hierarchy outlined below:
One kind of memory can suffer (due to a cognitive disease or physical damage) while others remain perfectly intact*. For example, people suffering amnesia can forget their relatives but recall how to operate a manual transmission.
Forms the basis for 'automatic' thought. We aren't really aware of implicit memory. For example, shifting gears in a manual car requires no front-brain effort because the sequence of operations is stored in implicit memory.
These are memories that can be brought to bear in logic and action. The hippocampus and medial temporal lobe are important for explicit memories*.
"General knowledge" is stored in semantic memory*. Knowledge is expressed by language, so an understanding of what words and word-structures mean (e.g. semantics) is required to store information that interfaces with the rest of the outside world. Generally we don't track where we obtained semantic memories as that would be overwhelming*. An example of semantic memory would be "how to perform a Riemann sum".
Stores specific events and incidents that occurred personally to an individual. Often the 'lessons' from these memories are transformed into fundamental knowledge and shift into semantic memory*.
Multiple trace theory (MTT) has its origins in pre-1900 Gestalt psychology and is a decent model that currently fits most of the data we have on the operation of human memory. The idea is that "every experience lays down a unique trace, and repetitions of an experience don't overwrite earlier traces; they simply lay down more, near-identical unique traces of their own*". MTT is not universally accepted, but it currently presents the most functional model with which we can understand memory.
An experience occurs and a trace is laid in the mind. All traces are not created equal. There are both "environmental factors" that cause an event to lay less of a trace in the mind and certain tricks that can aid memory by laying stronger traces or (more often) successive very unique traces that compound into a strong memory.
An understanding of these environmental factors and tools is very pragmatically useful. See my additional notes on the topic:
>> Memory Formation Tools and Notes
chmod 670 When a memory is brought into bear by conscious thought it is both readable and writable*. So pondering a memory is powerful but fraught with peril. One can update an old memory (for example, something in semantic memory when new data is learned or experience disproves and maxim) with new data. However, this can occur unconsciously too and over time the mind bends old memories to fit present needs. Autobiographical memory is, especially, goal oriented* and real memories can become corrupted to fit a narrative.
I like to think of chmod 670 for this. You (the user) can read and write memory. Your subconscious (the group) can read, write, and execute the memory (the latter in the case of implicit procedural memories like walking up a staircase). And thankfully the outside world can't read your memories or write to existing ones.
A natural function of the mind is to fill in the gaps in memories, as memory is fallible. This is a natural function of a healthy mind. Memory shouldn't be perfectly accurate (see the interesting case of Solomon Shereshevsky) so that we can effectively pursue pattern recognition. Therefore there will always be holes which can be filled by logic with decent accuracy*.