Okay, so rape is when someone touches your body in a way that you don't like or want, without asking you first. This is never okay and it's against the law.
If someone does this to you, it's important that you tell a grown up that you trust, like a parent or teacher, and they will help you. The grown up will call the police, who are people that help to make sure that everyone is being safe and following the rules.
In some places, there are extra laws that say that even if you say "yes" to someone touching you, it doesn't count as okay if you were forced or threatened to say yes. This is because it's important that everyone involved really wants to touch someone else's body in that way, and that no one is feeling scared or pressured into it.
Sometimes, people use drugs or alcohol to make someone else not able to say "no" to touching. This is also against the law and is called "date rape." People need to make sure that anyone they are touching with is totally okay with it, and if they're not sure, they should ask.
Remember, if anyone ever touches you in a way that you don't like or want, it's never your fault and you should tell a grown up that you trust right away.