I will give a description that is only partly accurate but I think helps separate concepts pretty well. It is some cross between an analogy of what is happening in memory and what is physically happening. Imagine that emotional memory and event memory are completely separate and independent. You can think of it as video and audio for a film, or text and illustration in a book. They can be related, and mostly are related, but they don't have to be. They are stored in different parts of the brain, though often with plenty of overlap. Yet what if the audio was noise? The sound of a car crash when the guy kisses the girl in a movie? How would that get stored? How would the brain put that together?
It might not put it together, which is part of why traumatic memories are unreliable, even when they are about indisputably real things.
Years ago I went out in my slippers in winter to the head of the driveway to adjust the trash barrels for pickup. I slipped and slammed my foot against a big chunk of ice, pulling the big toenail mostly off. I still wince from my right big toe all the way up my leg and even up my spine when I think of it. Small wonder, as it has never been quite right ever since. That toenail came mostly off and a new one grew in - sort of. That eventually grew out and another came in, looking very strange. This is the sixth toenail now, and it looks almost normal. But you can see how that wincing is a sort of mild PTSD, and a person who had been beaten as a child or suffered repeated injury could find themselves wincing frequently, enough to start interfering with functioning.
So now I will mention. It's actually the left big toe that was injured. There's no question of that, you can look at the toenail and see, even years later, that it's not right. Yet when I think of the incident, my brain tells me it was the right toe that was injured. Somehow the message got scrambled and stored improperly. Trauma does that. It's not linear.
Worse, when trauma has scrambled lots of your memories, you can get triggered - those are quite real - and be delivered into an inaccurate memory because it looked a lot like a previous one and your brain has traveled that route umpteen times. There are ruts in that road, your pickup just goes there more easily. It would take a conscious effort to override the ruts.
This has been an enormous problem in trying to prosecute child abusers and molesters. The memories of the victims are unreliable and thus weakened in court. Sometimes there are childhood ER records or photos someone took or other witnesses, but other times - the child, now grown, can be made to look like a liar, or at least inaccurate, on the witness stand. The perp goes free. Intense memory being what it is, it's doubly infuriating for the victim, who has vivid memories of the event and sometimes will not help the prosecution because they refuse to back down from what they are absolutely sure is true.
There is a subtler way that memory can go wrong. I have mentioned before, and it is becoming more widely known, that even though those of us who grew up with movies and TV automatically think of our memories as something like a film record, they are actually more like a computer (or graphing calculator) that reconstructs the memory from scratch each time, based on the previous times we have remembered it, especially the most recent. When we are done thinking about it we put it back in storage, where it lies unchanged. But while it is out and active, all bets are off. Things can get added in, things can drop out. Sometimes this is rather random, not according to any narrative direction from other parts of the brain. But for important memories that keep getting brought back, they get gradually adjusted to fit the story. The story can be very general: my sisters have always betrayed me. Or Men in STEM think women aren't quite as good. Narratives like that can have good supporting evidence. Contrary evidence might be acknowledged at first, especially if someone draws attention to it. Well, Meg did help you pay for a lawyer. Or But your first academic advisor said you were the best student he'd ever had. Yet without that help, there is not even any need for you to actively suppress the contrary information. You'll just do it naturally.
Consider, for example, when you get angry at someone and start rehearsing what trespasses they have trespassed against you. If you don't watch yourself - if you don't take active steps to try and make sure you have got the story right - you will have already shuffled the list of what they have actually done within a half hour, never mind a decade. Every incident you remember, at least at first, will be true. Nobody has to suggest a false memory to you. (Though if they do you might be too easily primed for it.)
You may remember exercises they gave in psychology or sociology classes, in which people are described, but slightly differently to everyone, then they decide who is going to get to stay on the island. The black drug addict turns out to be a doctor addicted to pain medication but sober the last two years. The unmarried mother of three turns out to be the widow of a police officer killed in the line of duty. It's supposed to show us all how ignorant and prejudiced we are. But it is valuable in showing that we really do see things differently when key bits of information are missing.
So when you and your sister remember borrowing each other's clothes without permission, and she remembers (correctly) that you did that a lot more often, while you remember (correctly) that she once damaged an expensive sweater of yours and never replaced it, and neither of you remember your own fault, it's going to look different fast.
False memories? Well, you've been unhappy for the last year and don't know why. A therapist makes a guess and suggests that you seem like other patients she has had who were molested. Huh. Maybe that's it. I mean, that would explain... and you are off and running. It does seem dreadfully unfair that victims who desperately need justice can get it. Yet when you recall that in almost no times and places in history have victims ever had much recourse, you can see why memory is not much advantage. Remember that you shouldn't get yourself into situations like X. Remember that those guys are violent. It's better to forget the details. Son #3, the older Romanian, has been actually comical in what he has forgotten about his traumatic past. In his first year in America he was in one of those youth group exercises about privilege. If someone made your dinner for you last night, take one step forward. If you live with both your parents at the same time, take two steps forward. He was near the front of the room! His new brother was actually a few steps in back of him! Then he laughed. "Oh, you mean ever in my life! I belong way back there!" and he went there laughing.The other Romanian called him a few months ago to let him know their aunt in Oradea had died. "Wait. We had an aunt in Romania?" His mother's sister, who brought up his sister. Forgotten.
I used to tell patients in the 1980s - and it was unpopular I got in minor trouble a couple of times - "If you were lucky enough to forget it the first time, don't go looking for it now." Exploratory therapy, which used to be the norm, is potentially catastrophic.