Well kiddo, have you ever heard of the internet? It's a place where people can share all sorts of stuff, like pictures, videos, stories, and more. Rule 34 is a kind of funny rule that people made up about the internet.
Basically, Rule 34 says that if you can think of something, there's probably a picture or video of it on the internet somewhere. And when we say something, we mean anything. Literally, anything.
So, when we talk about Rule 34 in relation to film, it means that there might be some movies or videos out there that show things that are not exactly appropriate for kids or for some grown-ups.
This rule is usually applied as a joke, but it also reminds us that even though the internet can be a fun and useful place, there are also things on it that we might not want to see. So, always be careful when using the internet and if you ever come across something that makes you uncomfortable or confused, talk to a grown-up who can help you out.