Okay kiddo, I'll try to explain it to you in a way that you can understand it.
You know how sometimes people believe things that aren't true? A conspiracy theory is something that some people believe even when there is no evidence to support it.
There is this idea called the "pizzagate conspiracy theory" that says important people and famous politicians like Hillary Clinton are really bad people who are part of a secret group that does really bad things like kidnapping and hurting children. The theory goes that they do these bad things in a pizza place called Comet Ping Pong, in Washington DC.
The truth is, there is no proof that any of this is true. In fact, it has been debunked by the police and the FBI.
It's important to make sure that we don't believe things that aren't true just because some people say it is. We should always try to find reliable sources and look at the evidence before making up our minds about things.