Superhuman strength is when a person is able to lift or carry very heavy things that normal people cannot. It's like when Superman is able to lift a car and throw it far away!
You know how we have muscles in our bodies that help us move around and do things like running, jumping, and lifting? Superhumans have muscles that are much stronger and more powerful than a regular person's muscles.
But how do they get these super-strong muscles? There are many different ways that superhumans could get their strength. Some might be born with special genes that give them extra strong muscles. Others might have been exposed to special powers or radiation that made them stronger.
Even though superhumans have super strength, they still need to be careful. Just like how you shouldn't lift something too heavy for your body, superhumans need to be aware of what their bodies are capable of. If they try to lift something that's too heavy, they could hurt themselves.
So, in short, superhuman strength is when someone has really, really strong muscles that can lift and carry things that are much heavier than what a regular person can handle.