Writing style is like how you choose to dress up your words when you write. It helps to make your writing unique and interesting to read. Just like how you choose your clothes depending on where you are going or how you want to feel, you can choose a writing style depending on what you want to say or how you want the reader to understand it.
If you want to write a spooky story, you might use a writing style that is very mysterious and creepy, using lots of dark and eerie words. Or if you want to write a happy story, you might use a writing style that is cheerful and upbeat, using lots of bright and positive words.
Sometimes, you might want to write in a way that makes your reader feel like they are right there with you, experiencing everything you are experiencing. Or you might want to write in a more formal way, like you're giving a presentation to a group of grownups.
Writing style can also include things like how long your sentences are, how you use punctuation, and how you break up your paragraphs. All of these things work together to make your writing sound like you and help your reader understand what you're trying to say.