Autobiografiction is a fancy way of saying a story that mixes real-life facts and made-up parts. Imagine you are telling a story about your day at school, but instead of just telling what happened, you also add some things that did not happen, like maybe you met an alien in the playground. It's like telling a lie, but your teacher will not be mad because it's part of the story!
Autobiografiction is when someone writes a book about their own life, but they add some pretend things too to make the story more interesting. They might talk about real things that happened to them, like when they went to the beach with their family or when they won a science project at school. But then they might also add some pretend things, like when they met a talking gorilla while exploring a jungle.
This type of story can be tricky because sometimes it is hard to tell what parts are true and what parts are made up. But, it can also be fun to read because it brings in real-life experiences and mixes them with imaginary adventures.