Okay, so let's say you have a toy that your parent doesn't want you to play with. They tell you to put it away and not touch it until they say it's okay. But you're really curious and you sneak it out to play with it anyways.
Now, let's imagine that this toy is actually something that's not allowed, like a toy gun that looks real. If the police come to your house and see you with it, they can take it away from you because it's illegal.
But what if the police didn't have the right to come into your house and take the toy gun away from you in the first place? That's kind of like what happened in the Mapp v. Ohio case.
Miss Mapp was a lady who the police suspected had some illegal things in her house. They didn't have a warrant, which is like a special paper that says they're allowed to search your house. Despite this, they broke into her house and found some illegal stuff, which they then used to arrest Miss Mapp.
Miss Mapp's lawyers said that the police shouldn't have been able to use the illegal stuff they found in her house because they didn't have a warrant. The Supreme Court, which is like the boss of all the courts in the country, agreed and said that the police have to follow the rules when they search someone's house or else the things they find can't be used as evidence in court. This is called the "exclusionary rule."
So, basically, the Mapp v. Ohio case helped to make sure that your rights to privacy are protected and that the police have to follow specific rules when they search your house. Kind of like how your parent has to tell you it's okay to play with the toy gun before you can take it out again!