Okay, a saga is like a really long story with lots of different events that happen to the same people or family. It's kind of like a big adventure book where you get to follow the characters through their whole lives.
Imagine you have a favorite character from a book, and you want to read about them going on lots of different adventures. A saga would be like taking all those adventures and putting them into one big book, so you can see how the character grows and changes over time.
Some sagas are based on real-life events or people, while others are made up by authors. In either case, they usually have lots of different plotlines or sub-stories that weave together to create one big picture of a place or time.
Basically, a saga is just a really, really long story that tells you all about a person or group of people, from the beginning of their story to the end.