Mutants are special beings in the Marvel Comics universe who are born with unique powers that make them different than normal humans. Think of them like being born with a special superpower, like how some kids might be really good at math or good at sports.
But what makes mutants unique is that their powers are often things that can't be explained by science or technology. For example, some mutants are able to control the weather or read people's thoughts. These powers are often seen as strange or scary to people who don't have them, and many people in the Marvel universe view mutants with suspicion and fear.
Because mutants are born with their powers, they didn't get them from any outside source like an experiment or radiation exposure. This makes them different from other superheroes like Spider-Man or the Hulk, who got their powers through accidents.
In the Marvel universe, being a mutant carries a lot of weight and can have serious implications for how you're treated by society. Many mutants are discriminated against or treated as outcasts because of their powers, while others find themselves valued as powerful heroes.
And while there are many different mutants in the Marvel universe, perhaps the most famous is the X-Men, a group of mutants who fight for equality and justice for all mutants.