This being top of some search results might indicate its popularity, and usefulness:
What Is the Mandela Effect?
Who was Alexander Hamilton? Most Americans learned in school that he was a founding father of the United States of America but that he was not a president. However, when asked about the presidents of the United States, many people mistakenly believe that Hamilton was a president. Why? If we consider a simple neuroscience explanation, the memory for Alexander Hamilton is encoded in an area of the brain where the memories for the presidents of the United States are stored. The means by which memory traces are stored is called the engram and the framework in which similar memories are associated with each other is called the schema. So when people try to recall Hamilton, this sets off the neurons in close connection to each other, bringing with it the memory of the presidents. (Though this is an oversimplified explanation, it illustrates the general process.)
This rings true to me, as when I had one dream (not having any particular meaning) I recall a chair and a stair being intertwined - with the obvious connection between the two when there wasn't really any other.
And these three, discussed later, also seem to me more likely to affect memory:
Confabulation: Confabulation involves your brain filling in gaps that are missing in your memories to make more sense of them. This isn't lying, but rather remembering details that never happened. Confabulation tends to increase with age.
Post-event information: Information that you learn after an event can change your memory of an event. This includes event subtle information and helps to explain why eyewitness testimony can be unreliable.
Priming: Priming describes the factors leading up to an event that affects our perception of it. Also called suggestibility and presupposition, priming is the difference between asking how short a person is, versus how tall a person is. Saying, "Did you see the black car?" instead of "...a black car?" makes a subtle suggestion that influences response and memory.
Although I have a few memories that definitely seem to be in error, I have an example of the second (involving another person and where I think he was mistaken) that seemed to come from how one might view an earlier experience, and what we should have done at the time but didn't - mountaineering as it happens - and where my memory (most likely to be true) came from what I was thinking at the time as much as the actual physical activity we were doing.
Apart from these, we all seem to develop holes in our memory as we age, and mostly I don't try to recall much from the past since I'm sure most of it has just vanished. The more solid memories have always been there.
