Pseudo-mythology is like making up stories that seem like they could be true but actually aren't. It's like pretending that something happened a long time ago, but it's not real like the stories your parents read to you before bed.
For example, some people might make up a story about a giant monster that lived in a forest and terrorized the people who lived nearby. Even though the story might sound exciting, it's not a real myth because it never actually happened.
Pseudo-mythology is often created for fun or entertainment, like in books, movies, or video games. It's like playing pretend and imagining things that never existed in real life.