Okay kiddo, let me explain Google and China to you like you're five years old. So, you know how when you want to find something on the internet, you can use Google to search for it, right? Well, a long time ago, Google wanted to be friends with China and let people there use Google too.
But China said "nope, we don't like some of the things that people can find on Google, so we're not going to let it be used here unless you follow our rules."
So, Google said "okay, let's work something out." But then China made some more rules that Google didn't like, so Google decided to leave China entirely.
Some people are still upset about this because they think that people in China should have the same access to information that people in other countries do. But for now, Google and China are not friends anymore.