Masculinism is the idea that boys and men should be treated fairly and given the same opportunities as girls and women. It's like making sure that boys don't feel left out or think that they can't do things just because they're boys.
Some people believe that girls and women have been given special treatment for a long time, and now it's time to focus on making things fair for boys and men too.
But it's important to remember that masculinism shouldn't be about putting down girls and women or making them feel bad. It's about making things equal for everyone. Just like how we want everyone to have the same chances to play at recess or get a turn with a toy, we want everyone to have the same chances in life too.