Question: While some dreams are just non-sensical randomness that it's really obvious aren't real, some of them are kind of realistic, like the type of dreams you don't know are dreams until you are awake. Some of my dreams I remember from ages ago but I remember them as dreams even though they were realistic and could make sense as something that actually happened. Also I have memories that I know happened but that could easily be mistaken as something I just dreamed up. So I wanted to know what exactly it is in our brain that helps us diniguish memories of real-ish dreams from just plain memories?

Wow, wow, wow, great question.
This is one of the fundamental questions for people who are interested in memory.
A recent study showed that you could actually alter someone’s recollection of events by implanting a “false” memory that is very close in details to the “real” memory.
https://theconversation.com/rewriting-memories-with-red-herrings-14495
Although this sounds really quite creepy and scary, this kind of discovery could really help people who are suffering from Post Traumatic Stress disorder, who are trapped re-living memories over and over again.
Your brain tries to tie lots of pieces of information together when it makes a memory, such as smell, sight, touch, sound to make a memory that is strong-this also means that these senses can be triggers for those memories when you remember something.
I hope this answers your question, though it still is not completely understood how our brains know this kind of thing!!!