The generation effect is when you remember things better if you come up with them yourself. Think about when your mom asks you to help make a grocery list. If you come up with some of the items on the list yourself, you'll probably remember those things better when you go to the store.
This is because your brain has to work harder to come up with the information, and when you work harder to remember something, it sticks in your brain better.
It's kind of like when you draw a picture or write a story. You'll remember it better because you had to think about it and create it yourself.
So, if you want to remember something really well, try coming up with it yourself instead of just reading or listening to someone else's ideas.