A Mary Sue is a fictional character who is unrealistically flawless and lacks meaningful flaws or weaknesses. They are often seen as an idealized version of the author and can be difficult for readers to relate to or engage with.
Avoiding creating a Mary Sue is important for writers who want to create believable and engaging characters. By giving characters flaws and weaknesses, writers can make them more relatable and interesting to readers. Additionally, avoiding Mary Sues can help writers create more realistic and believable stories.