Okay kiddo, have you ever heard of inheritance? It's when someone gives you something when they die, like money or a toy. Well, hard inheritance is when the person who dies gives the thing to you and says you can't change it.
For example, imagine your grandpa gives you his old teddy bear when he passes away, but he says you can never give it away or change its color. That's a hard inheritance, because he's given you something, but he's also given you rules about what you can and can't do with it. It's like a special gift that comes with strings attached.
In science, hard inheritance means that a living thing inherits a trait or characteristic from its parents and can't change it. Like if your mom has blue eyes and your dad has brown eyes, you might have blue eyes too and not be able to change them. That's because your eye color is part of your genetic makeup, and you inherit that from your parents.
So hard inheritance is when you get something, but you can't change it, whether it's a tangible object like a teddy bear or a genetic trait like eye color.